Abstract: A IP telephony service allows customers to form user groups. Each user group can include multiple members, each of whom have their own telephony device. Each user group is assigned a unique group identifier, which can be a telephone number. As a result, a single telephony device belonging to a member of a user group can be associated with its own unique telephone number, and the telephone number of the user group. This also means that a member's telephony device could be associated with multiple different billing accounts. The system allows a user to select which of multiple different billing accounts that are associated with his telephony device are to be billed for outgoing communications.