receiving a billing initiation request signal from a wireless data service device, wherein the wireless data service device is one of the following: an interworking function (IWF) unit and a packet data serving node (PDSN);

responsive to the received billing initiation request signal, producing a usage-amount data for the subscriber based on the amount of data traffic that is duplicated and transferred to a dedicated accounting device by a data transferring device, wherein the usage-amount data is configured to apply different data service charges to each of a plurality of service categories which are provided to the subscriber;

transferring, via a communication network the usage-amount data to a data service control point (DSCP);

receiving, via a communication network, balance exhaustion data from the DSCP, wherein the balance exhaustion data indicates that no balance for the prepaid subscriber remains;

transmitting, via a communication network, the balance exhaustion data to the wireless data service device, wherein the wireless data service device is configured to restrict the subscriber to use the wireless data service based on the balance exhaustion data, and wherein the wireless data service device is configured not to determine whether the balance has been exhausted; and

responsive to a billing end request signal received from the wireless data service device, transferring a billing request signal, indicative of a request to bill the subscriber for the usage-amount data to an authentication, authorization and accounting (AAA) unit.