The convergence of GSM networks and the examination of methods for collecting and processing the billing information are discussed. The billing data are collected via high-speed communication links using reliable data protocols such as X.25 and file transfer and management (FTAM). Using dedicated billing systems and the mobile network's charging tariffs, the collected billing data are centrally processed into subscriber invoices and bills. Though the tariffs for subscriber may become complicated, it may ultimately give the subscribers more control over the way they are charged for using the mobile voice and Internet services and the Quality of Service receive from the network operator.