Abstract: A claimed utility box design that can be connected to a mobile phone with V.92 data modem function and a landline house telephone which is unsupported by local telephone service provider. The utility box houses a claimed circuit design to control signal currents for both in-coming and out-going phone calls, and a claimed controller program to utilize the data modem function of a mobile phone for making out-going phone call for voice communication. With this utility box, a mobile phone user can answer and make phone call on a connected house landline telephone set that is not supported by the traditional landline phone company service.