1. A system for characterizing phone calls in a public switched telephone network (PSTN), having a plurality of switches interconnected by trunk lines and a plurality of customer premises in communication with the switches, to identify Data Service Providers comprising: monitoring means disposed at a first location for monitoring routing messages directed to the first location; generating means responsive to the monitoring means for generating a call record including a plurality of call defining elements, the call record being identified by a first call defining element; updating means for updating a plurality of call records stored at a storage location with the call defining elements of the generated call record; and analyzing means for analyzing at least one of the call defining elements of the plurality of call records to identify Data Service Providers.