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. <EOS>