Abstract: A method and a circuit arrangement for the implementation of services via a telecommunications network. The services are, for example, backward/forward tariffing and data documentation via a telecommunications network. Backward tariffing, for example, enables the called party to invoice to the calling party any desired amount for a service provided via a telecommunications network. The operator of the telecommunications network is instructed by the called party and the calling party to collect this amount from the calling party. The data documentation service allows contracts concluded by the called and calling parties over the telephone to be confirmed by a third party—telecommunications network—with regard to the fact that the contract has been entered into and, if requested by the calling party and the called party, with regard to the contents of the contract.