a method is disclosed for processing call data among telephone switching offices and a remotely situated data base system for deriving call service information needed to complete special service calls , such as inward wats calls to a destination specified by the derived information . a network of local and toll offices compiles a special service call message including a caller dialed 800 number and an originating area code for the inwats service and then transmits that message to the data base system over ccis facilities including signal transfer systems . at the data base , the message is translated into a directory - unlisted number identifying an inwats customer station designated to serve the call . before the call is switched through the toll switching network under control of the unlisted number , the open / closed and busy / idle conditions of the inwats station are checked at the data base to determine the availability of the station to serve the call . traffic data is accumulated at the data base by originating area code and by the unlisted inwats number . when the number of calls to the unlisted number per unit time exceeds a threshold , the data base instructs the telephone system to inhibit such calls from being served for a prescribed period .