Monitoring data transmissions in a telecommunication network between a service user computer belonging to a service user and a service computer. A service request message from the service user computer prompts an intermediate node in the telecommunication network, which intermediate node is arranged between the service user computer and the service computer providing the requested service, to transmit an intermediate-node service request message to the service computer. The intermediate node then receives a service message from the service computer, which service message includes user data for the requested service and a service use parameter associated with the service, and the intermediate node reads the service use parameter from the service message and transmits it to a central parameter storage system in the telecommunication network. The parameter storage system stores the service use parameter on a user related basis, and the intermediate node transmits the user data to the service user computer.