Abstract: A system and method for automatically and seamlessly routing telephone calls across a telephone network. The system includes a telephone network interface box having a computer, a master file and client file stored in the computer. The master file is dynamically linked to the client file at routing time to produce a selected client location telephone number which is transmitted across the telephone network. The system utilizes Automatic Number Identification to identify the calling party. The master file has a plurality of records having a telephone number and a spatial key and is updated frequently. The client file has a plurality of records having a spatial key and a client telephone number. Methods of generating client file records for both radius and polygon defamed service areas through an automated computer process are included in the present invention.