A method of providing access to telecommunication services involves receiving a routing information request for terminating a communication with a mobile station located within a visited geographic region, the routing information request including a directory number local to the visited geographic region. A subscriber identity associated with the received directory number is then dynamically selecting from an evaluation of a decision tree, the decision tree associating a reference directory number with a plurality of reference subscriber identities. Each reference subscriber identity is associated with a telecommunications service user, each user being registered to receive telecommunication services within a respective home geographic region, the home geographic region being different from the visited geographic region. The mobile station receives access to the telecommunication services within the visited geographic region via the selected subscriber identity.