A subscriber's line is associated with a prepaid long distance account.
When the subscriber attempts a long distance call, it is determined from
the dialed digits whether the attempted call is a long distance call. If
a long distance call is attempted, the subscriber's prepaid account is
checked to determine whether it has any remaining credits. If no credits
are remaining, the subscriber is so informed, and the call is
disconnected. If the subscriber has credits remaining, the call is
connected as long as credits are remaining in the prepaid account.