Abstract: In an embodiment, a mobile device that is configured to receive calls on a first telephone network via a first telephone number is configured to receive calls on a second telephone network via a second telephone number. A subscriber interface module (SIM) is installed into the mobile device enabling the mobile device to communicate with the second telephone network. A username, password, and telephone number for the second network are obtained. The mobile device registers the username, password, telephone number for the first network and telephone number for the second network with the first telephone network. A telephone call is received from the first telephone network and a personal identification code is employed to verify the registration.