Dialing PBX Extensions From Cell Phone

Embodiments of the present systems and methods may provide PBX functionality with mobile calling devices, such as cell phones. Embodiments may provide, for example, PBX functionality without the need to use land line (VoIP or PSTN, or any other) phones. For example, in an embodiment, a method of call completion may comprise receiving an indication of a called party phone to be dialed at a mobile device, determining, at the mobile device, whether the indication refers to an extension number of a private branch exchange or to a phone number in the public switched telephone network, and when the indication refers to an extension number of a private branch exchange dialing, at the mobile device, at least a phone number in the public switched telephone network in order to complete a call to the indicated called party phone.