A system and method provide a telecommunications extension service for a subscriber. The system allows a subscriber to identify one or more telecommunications units to serve as extensions of one of the subscriber's telecommunications units when a call is directed to the subscriber's telecommunications unit. A list of numbers associated with telecommunications units to serve as extensions is maintained by the subscriber and may be stored at a service control point. Upon receipt of a call directed to the subscriber's telecommunications unit, ringing is provided to the subscriber's telecommunications unit and the telecommunications units serving as extensions. After the call is answered by the first telecommunications unit to be answered, the remaining telecommunications units can join the in-progress call.