A system may include a first Internet Protocol Multimedia Subsystem (IMS) network comprising one or more devices configured to receive a first registration request for a first mobile directory number (MDN), associated with a subscriber, wherein the first MDN corresponds to a home mobile directory number with respect to the first IMS network; and register the first MDN with the first IMS network. The one or more device may be further configured to detect a service point trigger, associated with the subscriber, to register a second MDN, foreign to the first IMS network, with a second IMS network, in response to the first MDN being registered; and send a second registration request to the second IMS network, to register the second MDN with the second IMS network.