Method for operating a billing system associated with a mobile radio network for billing for tariffable use of data, and data transmission network

A method for operating a billing system associated with a mobile radio network for billing for tariff based use of data provided by a network-external data store, where the data are used based on retrieval using a mobile terminal belonging to a user of the mobile radio network, comprising:

• transmitting, by the mobile terminal, a user address, identifying the user, and a data identifier, identifying the data which are to be retrieved, to an intermediate node connected to the mobile radio network;
• generating, by the intermediate node, an anonymous user identifier from the user address using encryption;
• transmitting, by the intermediate node, the anonymous user identifier and the data identifier to the data store, as a result of which the data store is prompted to transmit a cost variable, associated with the retrieved data, and the anonymous user identifier to the billing system;
• using a key associated with the encryption to recover the user address from the anonymous user identifier;
• and
• using the user address and the cost variable to debit a cost account which is associated with the user.