The system, apparatus and method of the present invention provide telecommunication conferencing services in a multiple leg telecommunication session. One of the system embodiments includes a database and a switching center. The database has stored in a memory a plurality of secondary directory numbers and a conference parameter associated with a primary directory number. The switching center has an interface for receiving an incoming call leg designating the primary directory number and for determining whether the primary directory number and its associated plurality of secondary directory numbers are configured for a conference mode. When so configured for the conference mode, the switching center includes further instructions to process and route each outgoing call leg associated with each secondary directory number of the plurality of secondary directory numbers to form a plurality of outgoing call legs, to monitor answering of the plurality of outgoing call legs, and to connect an answered outgoing call leg, of the plurality of outgoing call legs, to the incoming call leg for a multiple leg telecommunication conferencing session.