The dual mode handset system provides unified cellular service and wire-line service with a single Directory Number assigned to the dual mode handset and a corresponding cordless base station that are connected to the subscriber's local wire-line (POTS line) connection to the telephone network. The dual mode handset is programmed to operate as a cordless telephone when in proximity of the cordless base station. The handset operates as a cellular telephone when it is out of reach of the cordless base station. The dual mode handset is assigned the same telephone number as the subscriber's connection to a local wire-line telephone switching system. Consequently, the Caller ID information is consistent on calls originated through the dual mode handset, regardless of whether the call passes through the cordless base station to the subscriber's connection to a local wire-line telephone switching system or the cellular network.