A method and system for streamlining the calculation of a rate for a prepaid wireless call is provided. A mobile subscriber can be billed at one rate when she is within her home network and at a different rate when she is roaming in another network or can be billed at a special rate if she is within a location subject to the special rate. A time period for charging a call is allocated by the Service Control Point (SCP) and reported to the Mobile Switching Center (MSC) in the case of an outgoing call or a Gateway Mobile Switching Center (GMSC) in the case of an incoming call. A message from the MSC or GMSC to the SCP reporting an expiration of the first time period can contain information regarding a location of the prepaid subscriber. Thus, the next time period allocated by the SCP for the call can be billed at a rate that reflects the mobile subscriber's location at that time as reported by the MSC or GMSC.