A mechanism enabling users roaming in a visited network to specify whether they prefer to dial numbers belonging to their home network in local format or in international format from the visited network. Restrictions based on the type of call, and the geographic locations and preferences of the users involved in the call, are correspondingly applied. Information about the location of the user, taking into account the access location and user preferences, is sent from a home subscriber server to a serving call session control function entity, both in the home network of the user.