Methods and systems for registering a phone device on a synthetic communication network are described. One implementation receives a request to connect the phone device to a synthetic communication network that transmits messages over a data network using one or more phone numbers from a voice network. A phone number and a country code associated with the phone device to be used for communications over the synthetic network are obtained. The phone number is normalized to a standard format distinguishing the resulting normalized phone number from international phone numbers using the synthetic network. Before the phone device is registered, an association between the normalized phone number and the phone device is verified by sending a verification message addressed to the phone device that loops back to the phone device. If the phone device confirms the verification as authentic, an authorization allows the phone device to communicate over the synthetic network.