Abstract: The present invention is directed to a billing system which provides the most cost-effective long-distance telephone service for long-distance telephone calls made by an account by analyzing long-distance telephone calls in the aggregate, comparing the cost thereof between at least two different providers, and charging the account based on the lowest cost. Providers of long-distance telephone services aggregate those long-distance telephone calls for which an account is responsible and determine the cost of service based either on mileage or aggregate time. In a first embodiment, the billing system compares the costs of service associated with two different service plans, both of which determine the cost of service based on mileage. In a second embodiment, the billing system compares the costs of service associated with two different service plans, one which determines the cost of service based on mileage, the other of which determines the cost of service based on aggregate time.