Method for realizing communication sessions using a telecommunications network and involving at least one user equipment, wherein - in order to establish a communication session regarding the user equipment - the user equipment initiates a signaling session using at least one register message and at least one invite message according to the session initiation protocol, SIP, wherein the signaling session is handled by a processing entity or functionality of the telecommunications network, wherein the method comprises the following steps: -- in a first step, the register message is received by the processing entity or functionality, and the processing entity or functionality generates or retrieves or requests a product identifier information, the product identifier information being indicative of a product alternative used by the user equipment out of a plurality of different product alternatives, -- in a second step, the product identifier information is transmitted to the user equipment, -- in a third step, the invite message is received by the processing entity or functionality, wherein the invite message comprises the product identifier information, and wherein the invite message is handled, by the processing entity or functionality, in dependence of the product identifier information received from the user equipment, wherein the handling or processing of the invite message by the processing entity or functionality is at least partly different dependent on the information content of the product identifier information, wherein, in dependence of the information content of the product identifier information, different components or microservices or sub-functions of the processing entity or functionality are used for at least partly handling or processing the corresponding request. wherein the method comprises the following steps: -- in a first step, the register message is received by the processing entity or functionality, and the processing entity or functionality generates or retrieves or requests a product identifier information, the product identifier information being indicative of a product alternative used by the user equipment out of a plurality of different product alternatives, -- in a second step, the product identifier information is transmitted to the user equipment, -- in a third step, the invite message is received by the processing entity or functionality, wherein the invite message comprises the product identifier information, and wherein the invite message is handled, by the processing entity or functionality, in dependence of the product identifier information received from the user equipment, -- in a first step, the register message is received by the processing entity or functionality, and the processing entity or functionality generates or retrieves or requests a product identifier information, the product identifier information being indicative of a product alternative used by the user equipment out of a plurality of different product alternatives, -- in a second step, the product identifier information is transmitted to the user equipment, -- in a third step, the invite message is received by the processing entity or functionality, wherein the invite message comprises the product identifier information, and wherein the invite message is handled, by the processing entity or functionality, in dependence of the product identifier information received from the user equipment, wherein the handling or processing of the invite message by the processing entity or functionality is at least partly different dependent on the information content of the product identifier information, wherein, in dependence of the information content of the product identifier information, different components or microservices or sub-functions of the processing entity or functionality are used for at least partly handling or processing the corresponding request.