When a roaming telephone user in a visited network dials a long-distance number, he is transferred to a substitute telephone number which is local to that network and belongs to a service center which can route his call efficiently and cost effectively. Typically, the visited network contacts the user's home network for permission to complete the long-distance call. When that happens, the home network obtains the substitute number from a database on a telephone number server, based upon the location of the visited network, and responds to the visited network, instructing it to forward the user's call to the substitute telephone number. When the service center receives the roaming user's telephone call, it contacts the telephone number server and obtains the original long-distance number, which is stored in the database in association with the substitute telephone number. The service center is then able to route the roaming users call efficiently and cost-effectively by making use of its base of service providers.