Abstract: A method is disclosed that normalizes a telephone number from a number of input sources into standardized E.164 “+” format so that the telephone number can be represented in a consistent format relative to the user's own mobile number MSISDN and used uniformly across different functional components in a communications system. The disclosure also describes a method for denormalizing a telephone number in the E.164 “+” format into a dial digit phone number sequence that can be used to successfully establish calls from a user terminal device and to route calls via optimal routes through a voice termination network.