A method of authenticating a caller and authorizing a callee in a user-device environment may include receiving, by a gateway, a logon request comprising information associated with a caller and determining whether the caller is a subscriber based on at least a portion of the received caller information. If the caller is a subscriber, an other gateway may receive information associated with a callee who belongs to a contact list associated with the caller. The other gateway may determine whether the callee is authorized based on at least the callee information and the caller information, and if the callee is authorized, a call between the caller and the callee may be connected.