Abstract: Information regarding the present location of a dual-mode (or multi-mode) mobile station with respect to a plurality of communication systems is timely maintained by facilitating automated contact information modifications via, for example, a mobility management server (30). In a preferred approach, upon receiving a message (11) evidencing the supported presence of a mobile station in a first communication system comprising a wireless wide area network, one automatically responds (12) by modifying such contact information as is retained in a Session Initiation Protocol registrar. Testing (21) can be utilized to assure the propriety of making such alterations and/or deletions.