METHOD FOR THE USE OF BOTH A PRIMARY TELEPHONE NUMBER AND A SECONDARY TELEPHONE NUMBER REGARDING A PARTNER OF A TELECOMMUNICATIONS NETWORK, TELECOMMUNICATIONS NETWORK OR SYSTEM, CALLER IDENTITY UNIT OR FUNCTIONALITY, COMPUTER PROGRAM AND COMPUTER-READABLE MEDIUM

Description

State of the art

[0001] In existing telecommunications networks, it is common for a subscriber to be permanently assigned a telephone number. It is also common for this telephone number to be known to other subscribers, or even required to be known if other subscribers (or other subscribers) wish to reach the subscriber in question by telephone (or by other means, such as using a messaging application, chat application, or the like).

[0002] When considering fixed-line telecommunications networks or fixed-line connections, such a functionality has developed historically and is related to the fact that originally such an assigned telephone number or landline telephone number was usually either assigned to a geographical location or at least partially related to a geographical location or region. When considering mobile networks or mobile communication networks, although the subscribers are locally mobile, a subscriber or a subscription is always assigned identification information (or reachability information) for identification within the telecommunications network (or mobile communication network) under consideration (usually in the form of a UICC module (universal integrated circuit card or SIM module (subscriber identity module), SIM card or USIM card) or an eSIM ("built-in subscriber identity module")."embedded subscriber identity module")), which must be communicated to other participants so that the participant in question can be reached by these other participants.

[0003] This technical functionality in known telecommunications networks is generally implemented in this way.

[0004] This also applies in principle to the situation where, for example (particularly in the case of subscribers to mobile communications networks), more than one subscription or more than one piece of identification information for identification within either a single telecommunications network or one subscription or piece of identification information within the telecommunications network and at least one further subscription or piece of identification information within a further telecommunications network is assigned to a telecommunications terminal: For each of these two or more subscriptions or pieces of identification information, it generally applies (in each case individually) that the respective telephone numbers are also known to other subscribers or even have to be known if such other subscribers (or further subscribers) wish to reach the subscriber in question by telephone (or by other means, for example using a messaging application, chat application or the like).

[0005] However, such telephone numbers are a personal matter and are subject to data protection, which is why the disclosure of telephone numbers or identification information for subscriptions adversely reduces the level of data protection.

[0006] EP3211872 discloses a prior art telephone connection setup in which the confidentiality of the main telephone number is maintained by the use of secondary / alias numbers. Disclosure of the invention

[0007] The invention is based on the object of providing a method for using both a primary telephone number and a secondary telephone number with respect to a subscriber of a telecommunications network, wherein a communication connection between the subscriber and another subscriber can be established by means of the telecommunications network, wherein the method makes it possible to increase the level of data protection in a comparatively simple and efficient manner.

[0008] The object is achieved according to the invention by a method according to claim 1.

[0009] According to the present invention, it is advantageously possible to avoid, in a comparatively simple manner, the mandatory forwarding of telephone numbers or identification information for subscriptions in order to enable communication between the subscriber and the other subscriber.

[0010] Every telephone connection, whether mobile or landline, generally has a dedicated telephone number that can be reached. In the case of mobile networks, this telephone number is called an MSISDN (Mobile Subscriber Integrated Services Digital Network Number) and corresponds to a mapping of the telephone number to the corresponding SIM card or the unique IMSI (International Mobile Subscriber Identity) contained therein.

[0011] It is common practice in telecommunications networks (e.g. since the introduction of ISDN landline connections) to book several numbers for one telephone connection in order to communicate these to different groups of subscribers if necessary, for example a work telephone number and a private telephone number; this made it possible to separate the needs accordingly. In mobile communication networks this is also possible in principle using the MSIDN, but its use is only rudimentary; for example, it is possible to assign an additional landline number to a mobile subscriber, but the mobile number is usually still shown as the Caller ID (CID) telephone number (i.e. the telephone number displayed when another subscriber is called). This means that the telephone numbers assigned in both the landline and mobile networks are generally relatively static and cannot be changed easily or at the initiative of the subscriber or user.Customers change or modify.

[0012] In addition, services are also known by means of which virtual telephone numbers can be assigned or received, so that such virtual telephone numbers are mapped or forwarded to a subscriber's landline or mobile connection. However, this also has the disadvantage that although the subscriber can be reached with a plurality or even a multitude of numbers, in the case of an outgoing call, the subscriber's own base number (or primary telephone number) appears as the caller ID telephone number (for the called party), which should not be disclosed.

[0013] Furthermore, services are also known by means of which the own telephone number (of the subscriber) can be hidden as a Caller ID telephone number and replaced with another number; however, this only allows an anonymization of the displayed telephone number of the caller (subscriber), a callback on this number, which is displayed as Caller ID, is not functionally possible, because the displayed Caller ID telephone number is in any case not assigned to the (calling) subscriber (i.e. either the telephone number is not assigned to any subscriber at all or any other, uninvolved subscriber is called).

[0014] However, phone numbers are a personal characteristic subject to data protection, similar to other personal information such as a date of birth or address. This information can potentially be used to steal and fake identities in order to carry out criminal or otherwise undesirable activities, such as stalking, etc.

[0015] Data protection is already a relevant issue, but so is the separation of professional, family, and leisure activities. Added to this are online activities where, for various reasons, a telephone number must be provided or requested in order to use a service. An important example of this is certainly two-factor authentication using a message (especially an SMS message, a short message system message) sent to a mobile phone number, via which a participant can receive such a message.

[0016] According to the invention, it is advantageously possible for separate telephone numbers to be used for many or all of such activities, without separate landline contracts (or landline connections) or mobile phone contracts (i.e., generally a plurality of SIM cards) being required for each of such different activities (by means of which, conventionally, essentially a single telephone number could be used (at least generally for outgoing calls).

[0017] Thus, the invention advantageously allows for greater control over the sharing of one's own telephone number. It also makes it possible to revoke a shared telephone number, for example, in the event of misuse (without being forced to immediately change the telephone number, which would in turn require all private and business contacts to be informed of the new telephone number and, if this were forgotten in an individual case, would prevent the person concerned from being able to reach the subscriber by telephone using the previous telephone number).

[0018] According to the invention, it is thus provided that a subscriber - in addition to using a primary telephone number (ie the conventionally known more or less only telephone number assigned to the subscriber) - is also able to use a secondary telephone number, but preferably a plurality or a multiplicity of secondary telephone numbers, ie for use within or as a subscriber of a telecommunications network for establishing, by means of which (optionally using further telecommunications networks) a communication connection can be established between the subscriber and another subscriber.

[0019] According to the invention, the telecommunications network comprises, is connected to, or has access to a caller identity unit or functionality.

[0020] According to the invention, the method for establishing the communication connection between the subscriber and the further subscriber comprises the steps of using the primary telephone number between the subscriber and the caller identity unit or functionality and using the secondary telephone number between the further subscriber and the caller identity unit or functionality.

[0021] As a result, the subscriber's primary telephone number is used only between the subscriber and the caller identity unit or functionality (or only needs to be used within this area). According to the invention, the secondary telephone number (which is, however, uniquely assigned to the subscriber (in the direction from the other subscriber to the other subscriber)) is used between the caller identity unit or functionality (of the telecommunications network or another telecommunications network) and the other subscriber. This means that the other subscriber can, for example, call the subscriber back using the secondary telephone number.

[0022] According to a preferred embodiment of the present invention, it is preferably provided that the communication connection between the subscriber and the further subscriber is established by a call being set up by the subscriber or being initiated by the subscriber, wherein initially - during the first step - the primary telephone number is used and subsequently - during the second step - the secondary telephone number is used, wherein in particular the secondary telephone number is used as the subscriber's caller ID used for the further subscriber.

[0023] According to a further embodiment of the present invention, it is preferably provided that the communication connection between the subscriber and the further subscriber is established by a call being set up by the further subscriber or being initiated by the further subscriber, wherein initially - during the second step - the secondary telephone number is used and wherein subsequently - during the first step - the primary telephone number is used.

[0024] Due to the exclusive use of the secondary telephone number in both embodiments with respect to the further subscriber, it is advantageously possible according to the invention for the further subscriber to receive no knowledge of the primary telephone number of the subscriber in a comparatively simple manner or to only receive the secondary telephone number when displaying the subscriber's caller ID, but nevertheless to have the option of reaching the subscriber at any time using the secondary telephone number, ie by the further subscriber setting up a call using the secondary telephone number.

[0025] According to a further embodiment of the present invention, it is preferably provided that the primary telephone number and / or the secondary telephone number is or are an MSISDN telephone number.

[0026] This makes it particularly advantageous according to the invention that the method according to the invention can be carried out simply and efficiently.

[0027] According to a further embodiment of the present invention, it is preferably provided that the primary and secondary telephone numbers are assigned to a telecommunications terminal assigned to the subscriber or to a subscription of the subscriber, wherein in particular the primary telephone number is not forwarded to the further subscriber and in particular is not known.

[0028] According to such an embodiment of the invention, it is advantageously possible for the primary telephone number to be protected from being passed on.

[0029] According to a further embodiment of the present invention, it is preferably provided that the caller identity unit or functionality with respect to the further subscriber has a contact book entry such that in the case of an outgoing communication connection from the subscriber to the further subscriber using the primary telephone number, the secondary telephone number is used instead of the primary telephone number and / or that in the case of an incoming communication connection from the further subscriber to the subscriber using the secondary telephone number, the communication connection is established with the subscriber.

[0030] As a result, according to such an embodiment of the invention, it is advantageously possible for the participant to use the method according to the invention in a comfortable manner, in particular without additional or at least without considerable additional effort.

[0031] According to a further embodiment of the present invention, it is preferably provided that the contact book entry is created automatically or can be generated manually, wherein in particular a plurality of different secondary telephone numbers can be used for different additional subscribers.

[0032] As a result, according to such an embodiment of the invention, it is advantageously possible for the method according to the invention to be used simply and effectively and furthermore for a plurality of secondary telephone numbers to be available (and assigned to the subscriber).

[0033] According to a further embodiment of the present invention, it is preferably provided that the contact book entry and / or the secondary telephone number -- has a limited period of validity and / or -- becomes invalid or becomes inactive at the initiative of the subscriber and / or at the initiative of the telecommunications network, or becomes invalid or becomes inactive for a specific, in particular recurring, period of time and / or -- for communication connections using telecommunications networks other than the telecommunications network, in particular for roaming situations,is usable or alternatively is not usable and / or -- is only usable for communication connections concerning voice connections or only for communication connections concerning data connections or for communication connections concerning both voice and data connections or is usable for communication connections concerning or using a specific application or group of applications and / or -- is restricted to use by the additional subscriber or by the additional subscriber and additionally one or more other subscribers, in particular a limited number of other subscribers and / or -- is invalidated or set to an inactive state for use by the additional subscriber or one or more other subscribers at the initiative of the subscriber and / or at the initiative of the telecommunications network or is set to an inactive state for use by the additional subscriber or one or more other subscribers or for a specific,in particular a recurring period of time is invalidated or placed in an inactive state and / or -- at the initiative of the subscriber and / or at the initiative of the telecommunications network, despite the secondary telephone number or corresponding contact book entry being invalid or placed in an inactive state for use by the other subscriber or one or more other subscribers, it is still usable for at least one specific other subscriber.

[0034] According to a further embodiment of the present invention, it is preferably provided that the primary telephone number is assigned to the subscriber or a telecommunications terminal on the basis of a subscription, wherein the primary telephone number is an MSISDN telephone number assigned to the telecommunications terminal and / or the subscription.

[0035] Furthermore, the object is achieved by a telecommunications network or a system according to claim 7.

[0036] It is therefore advantageously possible according to the present invention to provide a telecommunications network or system according to the invention corresponding to the method according to the invention.

[0037] The object is further achieved by a caller identity unit or functionality for use in a telecommunications network or system according to the invention.

[0038] Furthermore, the problem is solved by a computer program comprising instructions with the aid of which the steps of a method according to the invention can be carried out when the computer program is executed on a programmable device, in particular on a network node of the telecommunications network or a caller identity unit or functionality.

[0039] Furthermore, the object is achieved by a computer-readable medium provided for storing a computer program, or data carrier signal provided for transmitting a computer program, wherein the computer-readable medium or the data carrier signal stores or transmits the computer program according to the invention or wherein the computer-readable medium or the data carrier signal stores or transmits the part of the computer program according to the invention to be executed on a programmable device, in particular on a network node of the telecommunications network or a caller identity unit or functionality.

[0040] Further details, features, and advantages of the invention will become apparent from the drawings and the following description of preferred embodiments with reference to the drawings. The drawings merely illustrate exemplary embodiments of the invention, which do not limit the essential inventive concept. Short description of the drawings

[0041] Figure 1 schematically shows a telecommunications network with one subscriber and another subscriber, wherein the telecommunications network includes a caller identity unit or functionality. Figure 2 shows a schematic detail of the caller identity unit or functionality. Embodiments of the invention

[0042] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0043] The present invention will be described with reference to specific embodiments and with reference to specific drawings, but the invention is not limited thereto, but only by the claims. The described drawings are merely schematic and non-limiting. In the drawings, the size of some elements may be exaggerated and not drawn to scale for illustrative purposes.

[0044] When an indefinite or definite article is used when referring to a single noun, e.g. "ein", "eine", "der", "die", "das", this includes a plural of that noun unless explicitly stated otherwise.

[0045] Furthermore, the terms first, second, third, and the like are used in the specification and claims to distinguish between similar elements and not necessarily to describe a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein may function in a different order than that described or illustrated herein.

[0046] In Figure 1 A telecommunications network 100 with a subscriber 20 and another subscriber 21 is shown schematically. In the exemplary representation according to Figure 1The telecommunications network 100 is shown as a mobile radio communication network, comprising an access network 110 and a core network 120, wherein the access network has a first base station device 111 and a second base station device 112. Each of the base station devices 111, 112 has, schematically indicated by a dashed circle, a radio coverage area or serves or covers this, wherein the first base station device 111 serves or covers a first radio coverage area 11 and the second base station device 112 serves or covers a second radio coverage area 12. The telecommunications network 100, or in particular the core network 120, has in Figure 1In the example shown, the telecommunications network 100 has or includes a caller identity unit or functionality 150. Alternatively, to the telecommunications network 100 having the caller identity unit or functionality 150, it can also be provided according to the invention that the caller identity unit or functionality 150 is not part of the telecommunications network 100, but rather the telecommunications network 100 is merely connected to the caller identity unit or functionality 150 or has access to the caller identity unit or functionality 150.

[0047] According to the invention, it is provided that the subscriber 20 (of the telecommunications network 100, ie in particular a landline subscriber or a mobile subscriber, ie for example a telecommunications terminal of a user of the telecommunications network 100) is assigned both a primary telephone number 220 and a secondary telephone number 221 and by means of the telecommunications network 100 a communication connection can be established between the subscriber 20 and a further subscriber 21, in particular using (in particular simultaneously) both the primary telephone number 220 and the secondary telephone number.According to the present invention, it is proposed that (to establish the communication connection between the subscriber 20 and a further subscriber 21) in a first step the primary telephone number 220 is used between the subscriber 20 and the caller identity unit or functionality 150, and in a second step the secondary telephone number 221 is used between the further subscriber 21 and the caller identity unit or functionality 150. In this case, for an outgoing call (from the perspective of the subscriber 20) or an outgoing communication connection (for example a telephone call or a message) to the further subscriber 21, the first step is generally carried out first, followed by the second step, whereas for an incoming call or incoming communication connection (from the perspective of the subscriber 20) from the further subscriber 21of an incoming communication connection (such as a telephone call or a message), the second step is generally carried out first, followed by the first step. In other words, the communication connection between the subscriber 20 and the further subscriber 21 is established by a call being set up by the subscriber 20 or being initiated by the subscriber 20 (outgoing call from the perspective of the subscriber 20), whereby initially - during the first step - the primary telephone number 220 is used and subsequently - during the second step - the secondary telephone number 221 is used, whereby in particular the secondary telephone number 221 is used as the caller ID of the subscriber 20 used for the further subscriber 21.

[0048] Analogously, the communication connection between the subscriber 20 and the further subscriber 21 is established by a call being set up by the further subscriber 21 or being initiated by the further subscriber 21 (incoming call from the perspective of the subscriber 20), whereby initially - during the second step - the secondary telephone number 221 is used and whereby subsequently - during the first step - the primary telephone number 220 is used.

[0049] Both the incoming call to subscriber 20 and the outgoing call from subscriber 20 are in Figure 1 represented or indicated by arrows between the subscribers 20, 21 and the caller identity unit or functionality 150, wherein the call originating from the subscriber 20 is represented by solid line arrows and the call incoming to the subscriber 20 is represented by dotted line arrows.

[0050] According to the invention, it can thus be ensured in particular that the primary telephone number 220 is not forwarded to the further subscriber 21 and in particular is not known, but that the accessibility of the subscriber 20 by the further subscriber 21 is nevertheless guaranteed in the form of the secondary telephone number 221.

[0051] In particular, according to the invention, the primary and secondary telephone numbers 220, 221 are assigned to a telecommunications terminal assigned to the subscriber or to a subscription of the subscriber 20.

[0052] According to the invention, it is particularly preferably provided that the caller identity unit or functionality 150 is assigned to the subscriber 20 and has a contact book entry with regard to the further subscriber 21 such that in the case of an outgoing communication connection from the subscriber 20 using the primary telephone number 220 to the further subscriber 21, the secondary telephone number 221 is used instead of the primary telephone number 220 and / or that in the case of an incoming communication connection from the further subscriber 21 using the secondary telephone number 221 to the subscriber 20, the communication connection is established with the subscriber 20.By means of the caller identity unit or functionality 150 and in particular the contact book entry (relating to the further subscriber 21), it is thus comparatively easy to implement the conversion from the use of the primary telephone number 220 between the subscriber 20 and the caller identity unit or functionality 150 on the one hand to the use of the secondary telephone number 221 between the caller identity unit or functionality 150 and the further subscriber 21.

[0053] In particular, the invention provides for the contact book entry to be created automatically or to be manually generated. In particular, a plurality of different secondary telephone numbers can be used for different additional subscribers; for example, each different additional subscriber receives a different secondary telephone number.

[0054] The caller identity unit or functionality 150 is also referred to below as Caller ID Enhancement Service (CIDES) and is in Figure 2shown schematically: When a subscriber 20 (for example a SIM card holder) makes a request, by calling an (external) telephone number which is not stored in the user’s address book (i.e. of the first subscriber 20, i.e. in the contact book of the caller identity unit or functionality 150 for this subscriber 20) (i.e. corresponds to a new, unknown telephone number), a new (in particular temporary and / or dynamic) secondary telephone number (in particular an MSISDN 2) is generated by manually generating a new address book entry (contact book entry which is to be linked to a new (secondary) telephone number as a call signaling number (caller ID)) and this is communicated to a database and / or the caller identity unit or functionality 150 or also the home location register (HLR) of the mobile network operator. The mapping orthe mapping of the (newly generated) secondary telephone number (MSISDN 2) of the user (i.e. which is assigned to the subscriber 20 with reference to the further subscriber 21) to the primary telephone number 220 of the subscriber 20 or to another identification information of the subscriber 20, for example the IMSI.

[0055] Subsequently, the caller identity unit or functionality 150 or the CIDES establishes the call to the unknown / new telephone number (i.e., to the additional subscriber 21) and generates the caller ID (CID) with the new MSISDN 2 (i.e., with the new secondary telephone number 221), which is then displayed upon receipt of the call to the called user (i.e., the additional subscriber), typically on their telephone display.

[0056] If the additional subscriber (i.e. User 2) makes a call back to this telephone number shown in the display, i.e. the displayed caller ID (MSISDN 2 or secondary telephone number 221), due to the registration of this secondary telephone number 221 (or MSISDN 2) in the database or in the caller identity unit or functionality 150 (or in the carrier HLR) of the telecommunications network 100, this call is correctly forwarded to the correct IMSI and thus to the correct SIM card or to the correct telecommunications terminal or plurality of telecommunications terminals of the subscriber 20, i.e. the telephone of the subscriber 20 (User 1) rings, and the additional subscriber 21 (User 2) has called the secondary telephone number 221 (MSISDN 2).

[0057] In particular, if a callback to the secondary telephone number 221 (MSISDN 2) (assigned to subscriber 20, i.e., User 1) is successful and answered, this MSISDN number is linked and synchronized with the telephone number of User 2 (i.e., with the (primary or secondary) telephone number assigned to the other subscriber 21) in the address book or contact book, so that for future calls (in particular from User 1 (subscriber 20) to User 2 (subscriber 21), the correct MSISDN (in this example: MSISDN 2) is always used for a call or to transmit the Caller ID). According to the invention, the privacy of subscriber 20 (i.e., User 1) thus remains intact in an advantageous manner, since the primary telephone number 220 (or MSISDN 1) is not disclosed as the Caller ID.

[0058] According to the invention, it is particularly provided that the new secondary telephone number or dynamic MSISDN 2 can be handled flexibly, for example, has a limited lifespan, based on e.g. the following

[0059] Features: -- when the (new) secondary telephone number is used for incoming or outgoing calls, the lifetime or expiry period is restarted; if no incoming or outgoing call is made using this telephone number within a predefined time window (iethere is no telephone contact between subscriber 20 and the other subscriber 21 in this time window), this number expires automatically and can no longer be used; -- the predefined time window can be a period of time defined by the user in which the secondary telephone number should be valid; -- the predefined time window can be a period of time defined by the network operator in which the secondary telephone number should be valid; -- the usability of the secondary telephone number can be determined by further parameters and a corresponding set of rules, such as: -- roaming possible / not possible; -- voice calls or only data / SMS sending / receiving possible; -- usage periods or geographical restrictions, e.g. only valid in a certain geographical location area (home zone, office, etc.).

[0060] According to the invention, it is particularly preferred that the contact book entry and / or the secondary telephone number 221 -- has a limited period of validity and / or -- becomes invalid or is rendered inactive at the initiative of the subscriber 20 and / or at the initiative of the telecommunications network 100 or becomes invalid or is rendered inactive for a specific, in particular recurring, period of time and / or -- for communication connections using telecommunications networks other than the telecommunications network 100, in particular for roaming situations,is usable or alternatively is not usable and / or -- is only usable for communication connections concerning voice connections or only for communication connections concerning data connections or for communication connections concerning both voice and data connections or is usable for communication connections concerning or using a specific application or group of applications and / or -- is restricted to use by the further subscriber 21 or by the further subscriber 21 and additionally one or a plurality of other subscribers, in particular a limited number of other subscribers and / or -- at the initiative of the subscriber 20 and / or at the initiative of the telecommunications network 100 is invalid or is put into an inactive state for use by the further subscriber 21 or one or a plurality of other subscribers or for a specific,in particular a recurring period of time is invalidated or placed in an inactive state and / or -- at the initiative of the subscriber 20 and / or at the initiative of the telecommunications network 100, despite the secondary telephone number 221 or corresponding contact book entry being invalid or placed in an inactive state for use by the other subscriber 21 or one or more other subscribers, it is still usable for at least one specific other subscriber.

[0061] Thus, according to the invention, it is advantageously possible for the caller identity unit or functionality 150 or the CIDES to also be used for other technical features, such as: -- the creation of MSISDNs with a limited validity from the outset (e.g. 24 hours) -- the implementation of a rule generation mechanism (rule engine) to define the permitted use of telephone numbers, e.g. this number does not work / only for WhatsApp or roaming etc. -- the principle of number blocking is put in the hands of the user, in order to prevent unwanted calls, for example, it is possible to block or delete the corresponding secondary telephone numbers (as virtual telephone numbers ("MSISDN X")).

[0062] This makes it particularly advantageous according to the invention that -- the subscriber 20 can decide for themselves which telephone number (or which secondary telephone number or even whether the primary telephone number) is or should be shared and how this subscriber 20 can be reached, for example under one of the respective secondary telephone numbers; -- the (secondary) telephone number (or the secondary telephone numbers) can be withdrawn at any time; -- a set of rules can be used to determine certain factors such as how the new telephone number can be reached or not; -- the routing itself takes place in the telecommunications network or in the cloud and does not affect the caller or the called party.

Claims

1. Method for using both a primary telephone number (220) and a secondary telephone number (221) in relation to a subscriber (20) to a telecommunications network (100), the telecommunications network (100) being a mobile communications network, and the primary telephone number (220) and the secondary telephone number (221) being MSISDN telephone numbers, wherein, by means of the telecommunications network (100), a communication connection can be established between the subscriber (20) and a further subscriber (21), the subscriber (20) and the further subscriber (21) being connected to a core network (120) of the telecommunications network (100) via an access network (110) of the telecommunications network (100), wherein the telecommunications network (100) has or is connected to or has access to a caller identity unit or caller identity functionality (150), wherein the method comprises the following steps for establishing a communication connection between the subscriber (20) and the further subscriber (21): - in a first step, the primary telephone number (220) is used between the subscriber (20) and the caller identity unit or caller identity functionality (150), - in a second step, the secondary telephone number (221) is used between the further subscriber (21) and the caller identity unit or caller identity functionality (150), wherein the communication connection is established between the subscriber (20) and the further subscriber (21) in that a call setup is performed at the subscriber (20) or initiated at the subscriber (20), the first telephone number (220) being used initially - during the first step - and the secondary telephone number (221) being used later in time - during the second step - as a caller ID of the subscriber (20) used towards the further subscriber (21), the secondary telephone number (221) being recorded in a home location register, HLR, of an operator of the telecommunications network (100), a further communication connection being established between the subscriber (20) and the further subscriber (21) on the basis of the secondary telephone number (221) recorded in the home location register in the event of a return call from the further subscriber (21).

2. Method according to claim 1, characterised in that in the primary and secondary telephone number (220, 221) are assigned to a telecommunications terminal associated with the subscriber or to a subscription of the subscriber (20), in particular the primary telephone number (220) not being passed on to and in particular not being known to the further subscriber (21).

3. Method according to either of the preceding claims, characterised in that the caller identity unit or caller identity functionality (150) has a contact book entry in relation to the further subscriber (21), in such a way that, in the event of an outgoing communication connection from the subscriber (20) to the further subscriber (21) using the primary telephone number (220), the secondary telephone number (221) is used instead of the primary telephone number (220), and / or, in the event of an incoming communication connection from the further subscriber (21) to the subscriber (20) using the secondary telephone number (221), the communication connection to the subscriber (20) is established.

4. Method according to any of the preceding claims, characterised in that the contact book entry is produced automatically or can be generated manually, in particular a plurality of different secondary telephone numbers being usable for different further subscribers.

5. Method according to any of the preceding claims, characterised in that the contact book entry and / or the secondary telephone number (221) - has a time-limited validity duration, and / or - is made invalid or placed in an inactive state or is made invalid or placed in an inactive state for a particular, in particular repeating, time period at the initiative of the subscriber (20) and / or at the initiative of the telecommunications network (100), and / or - is usable or alternatively not usable for communication connections using further telecommunications networks as the telecommunications network (100), in particular for roaming situations, and / or - is usable only for communication connections for voice connections or else only for communication connections for data connections or for communication connections for both voice and data connections or is usable for communication connections for or using a particular application or group of applications, and / or - is limited to use by the further subscriber (21) or else by the further subscriber (21) and additionally by one or more other further subscribers, in particular a limited number of other further subscribers, and / or - is made invalid or placed in an inactive state for use by the further subscribers (21) or by one or more other further subscribers or is made invalid or placed in an inactive state for a particular, in particular repeating, time period at the initiative of the subscriber (20) and / or at the initiative of the telecommunications network (100), - can still be used for at least one particular further subscriber, at the initiative of the subscriber (20) and / or at the initiative of the telecommunications network (100), in spite of a secondary telephone number (221) or corresponding contact book entry which has been made invalid or placed in an inactive state for use by the further subscriber (21) or one or more other further subscribers.

6. Method according to any of the preceding claims, characterised in that the primary telephone number (220) is assigned to the subscriber (20) or to a telecommunications terminal on the basis of a subscription, the primary telephone number (220) being an MSISDN telephone number assigned to the telecommunications terminal (20) and / or to the subscription.

7. Telecommunications network (100) or system for using both a primary telephone number (220) and a secondary telephone number (221) in relation to a subscriber (20) to a telecommunications network (100), the telecommunications network (100) being a mobile communications network, and the primary telephone number (220) and the secondary telephone number (221) being MSISDN telephone numbers, wherein, by means of the telecommunications network (100), a communication connection can be established between the subscriber (20) and a further subscriber (21), the subscriber (20) and the further subscriber (21) being connected to a core network (120) of the telecommunications network (100) via an access network (110) of the telecommunications network (100), wherein the telecommunications network (100) has or is connected to or has access to a caller identity unit or caller identity functionality (150), wherein, for establishing a communication connection between the subscriber (20) and the further subscriber (21), the telecommunications network or system is configured in such a way that: - the primary telephone number (220) is used between the subscriber (20) and the caller identity unit or caller identity functionality (150), - the secondary telephone number (221) is used between the further subscriber (21) and the caller identity unit or caller identity functionality (150), wherein the telecommunications network (100) is configured in such a way that - if the communication connection is established between the subscriber (20) and the further subscriber (21) in that a call setup is performed at the subscriber (20) or initiated at the subscriber (20) - the first telephone number (220) is used initially between the subscriber (20) and the caller identity unit or caller identity functionality (150), and the secondary telephone number (221) is used later in time between the caller identity unit or caller identity functionality (150) and the further subscriber (21) as a caller ID of the subscriber (20) used towards the further subscriber (21), the secondary telephone number (221) being recorded in a home location register, HLR, of an operator of the telecommunications network (100), in such a way that a further communication connection is established between the subscriber (20) and the further subscriber (21) on the basis of the secondary telephone number (221) recorded in the home location register in the event of a return call from the further subscriber (21).

8. Caller identity unit or caller identity functionality (150) for use in a telecommunications network (100) or in a system according to claim 7.

9. Computer program comprising commands by means of which the steps of a method according to any of claims 1 to 6 can be carried out when the computer program is run on a programmable device, in particular on a network node of the telecommunications network (100) or a caller identity unit or caller identity functionality (150).

10. Computer-readable medium, provided for storing a computer program, or data carrier signal, provided for transmitting a computer program, wherein the computer-readable medium or data carrier signal stores or transmits the computer program according to claim 9, or wherein the computer-readable medium or data carrier signal stores or transmits the part of the computer program according to claim 9 which is to be run on a programmable device, in particular on a network node of the telecommunications network (100) or a caller identity unit or caller identity functionality (150) .