A method and system of utilizing a secondary telephone line service, and in one embodiment encompasses analyzing a dialing sequence to convert from utilizing the secondary telephone line service to utilizing a primary telephone line service without the use of a manual override. By referencing a database of numbers, the present invention is able to determine if an outgoing service request is compatible with a preferred interface (e.g., the secondary interface), and, if not, to direct the outgoing service request to another interface (e.g., the primary interface, such as a POTS network).