A method for communicating in a communication system, in particular an IMS based communication system, wherein the system comprises : at least one client device to which at least two public identities are associated, wherein the client devices is configured to register to telecommunication services provided by the communication system with a least one of its public identities of a user; a network entity that is configured to assign public identities to telecommunication services and to control the communication; the method comprises the following steps: • Requesting a telecommunication service of the communication system by a first client device or requesting a communication with the first client device by a foreign client device, wherein the request is associated to the one of the public identities of the first client device; • Sending the request to the network entity; • Resolving the request by the network entity by selecting in a database an entry that assigns the requested telecommunication service to the one of the public identities of the first client device; characterized in that the entry comprises an additional individual tag that is configured to link the telecommunication service to one or several public identities out of a set of the at least two public identities of the user, wherein the individual tag is created during a registration process of the first client device for the telecommunication service, wherein the individual tag is created by the network entity, wherein the network entity detects if the first client device that performs the registration process for data communication service is a non single-registration, non-SR, client device and only creates the individual tag and stores it in the database for non-SR clients device. wherein the system comprises : at least one client device to which at least two public identities are associated, wherein the client devices is configured to register to telecommunication services provided by the communication system with a least one of its public identities of a user; a network entity that is configured to assign public identities to telecommunication services and to control the communication; the method comprises the following steps: • Requesting a telecommunication service of the communication system by a first client device or requesting a communication with the first client device by a foreign client device, wherein the request is associated to the one of the public identities of the first client device; • Sending the request to the network entity; • Resolving the request by the network entity by selecting in a database an entry that assigns the requested telecommunication service to the one of the public identities of the first client device; • Requesting a telecommunication service of the communication system by a first client device or requesting a communication with the first client device by a foreign client device, wherein the request is associated to the one of the public identities of the first client device; • Sending the request to the network entity; • Resolving the request by the network entity by selecting in a database an entry that assigns the requested telecommunication service to the one of the public identities of the first client device; characterized in that the entry comprises an additional individual tag that is configured to link the telecommunication service to one or several public identities out of a set of the at least two public identities of the user, wherein the individual tag is created during a registration process of the first client device for the telecommunication service, wherein the individual tag is created by the network entity, wherein the network entity detects if the first client device that performs the registration process for data communication service is a non single-registration, non-SR, client device and only creates the individual tag and stores it in the database for non-SR clients device. <EOS>