The inventive method enables existing contracts between a user and a telecommunications network operator to be enlarged by a user dialling into a customer subscription and administration server (CSAS). The access procedure of the existing contract relation is used for authenticating the user. The subscription of new contract components, such as clearing of a new terminal for instance that has been purchased by dispatch is carried out in a menu-controlled manner and by means of instruction texts and tactile inputs. The aim of the invention is to authenticate the calling user, authorise the additional contracts, changes and services which can be subscribed and administered by the corresponding user and store newly subscribed or changed contracts and services. The CSAS is connected to the corresponding data bases of the telecommunications network, such as CCBS, CDB and HLR. IP dialling options are optionally provided by means of the telecommunications network and/or the public internet. The inventive method, inter alia and especially, optimises procurement of a second or third appliance for family members or to be used as a pool appliance in small enterprises. Personal appearance at the POS involving passport control and the complicated procedures for setting up and verifying a contract can thus be avoided in the future.