A system for processing wireless calls allows subscribers to port from one wireless service provider to another. Each mobile switching center stores a table containing a list of office codes for various directory numbers. Each office code in the table has a corresponding entry that indicates the portability of the office code. In addition, each office code has a corresponding entry that indicates whether the office code was originally assigned to the mobile switching center. When a call made to a directory number is routed to the mobile switching center, the switch accesses the table and references the office code of the directory number. If the office code is not portable and not originally assigned to the switch, the switch routes the call to the switch servicing the call. If the office code is not portable but originally assigned to the switch, the switch accesses a Home Location Register to determine the current status of the subscriber. If the office code is portable, the switch queries a Number Portability Database to obtain a local routing number, if available. Where no local routing number is provided, the switch queries the Home Location Register.