Patent ID: 8494499

Claim:
A system for achieving a Call Back service, the system comprising a callback center and an online charging system (OCS) module, wherein the callback center is configured to receive a callback request, acquire call duration and a roaming number, call a calling party and/or a called party of the callback request by using the roaming number, associate the calling party and the called party, adjust charging duration of a firstly called party, and notify the OCS module to deduct charges for the calling party/called party; and the OCS module is configured to allocate the call duration for the calling party/called party and deduct charges for the calling party/called party of the Call Back service; the callback center comprises an unstructured supplementary service (USSD) module, a callback module and a roaming number acquisition module, wherein the USSD module is configured to receive the callback request, judge whether the called party of the callback request is an OCS subscriber, acquire location information of the one of the calling party and the called party of the callback request which is the OCS subscriber, and send the callback request and the location information to the callback module; the callback module is configured to acquire the call duration of the calling party/called party, notify the roaming number acquisition module to acquire the roaming number of a subscriber, send to the MSC the information required by calling the calling party/called party, adjust the charging duration of the firstly called party, and notify the OCS module to deduct charges for the calling party/called party; and the roaming number acquisition module is configured to acquire the roaming number of the subscriber according to the location information of the subscriber after receiving a notification from the callback module, and send the roaming number of the subscriber to the callback module; wherein the roaming number acquisition module and the callback module use an internal message to interact with each other; and the callback center and the OCS module use a standard Diameter credit control protocol to transfer messages there between.