A method of reassigning user data in a communications system is disclosed, with a plurality of identities for each user. The method includes storing in a user information store the plurality of identities in association with a first serving controller, the plurality of identities being associated with respective registration statuses selected from a registered status and an unregistered status; detecting that the user has requested registration to a second serving controller using one of the identities; and issuing a registration termination request identifying each identity, which has been newly assigned to the second serving controller as a result of the requested registration. Responsive to the registration termination request, re-registration notification is issued to the user and all identities of the said user from the first serving controller are dissociated.