Abstract: A gateway unit which acts to provide interoperability between disparate mobile communications networks. The gateway unit provides the necessary protocol conversions between the different mobile networks. The gateway unit can be a stand-alone unit or co-located with a mobile switching center (MSC) wihtin North America or in foreign country. In each case, the gateway unit serves as an interconnection point between two or more networks. For example, the gateway unit converts messages from European networks, which use the International Telecommunications Union (ITU) and mobile global title (MGT) protocols to North American networks, which use the American National Standards Institute (ANSI) and international mobile station identity address (IMSI) protocols, and vis versa. The gateway unit preferably includes the elements of a processor, software and memory, all of which could be provided on a circuit board or in a conventional personal computer.