A telecommunications system is disclosed that enables a user to pair a desk set that is an extension of a private-branch exchange with a cell phone that is accessible via the Public Switched Telephone Network. One feature of the telecommunications system enables a call that is directed to the user's desk set to be automatically forwarded to the user's cell phone. This is advantageous to the user because it provides the illusion to the caller that the user is physically in his or her office when they are not necessarily there. A similar feature also provides the illusion when a third party initiates a call that connects the user's cell phone to a called party. Such a third party includes a computer telephony application in a telephone telemarketing center, which automatically places many outgoing telephone calls.