Updating the preferred routing information in a mobile telecommunication apparatus

摘要

A mobile telephone in a cellular telecommunications system uses data stored in a SIM cards select network for registration and to perform optimised call routing to a call destination. If data relevant to networks which are currently available is not stored, a request message is sent to a control centre and updating information received in a response message. The subscriber identity data stored in a memory file of the SIM can also be replaced to enable a preferred subscriber identifier to be used with the currently registered network, selection being made using a look-up table (201) updated when required using request and response messages. Greater control of the network selection and cost saving by avoiding roaming agreements are thereby achievable.