By default all Nokia Lumia phones are set to automatically correct the dialing code when roaming. This will also apply to a phone that has been used on a different network than the current one, to correct this here are the guides below :-
- If you have been roaming, deactivate your roaming, switch off and on your handset, the phone will then register the current network as your home network. This will deactivate the dialing code request.
- To remove/ deactivate this feature permanently follow these steps, Dialer(where you access your dialing pad)>>Options(3 dots at the bottom/top right-model dependent)>>Call Settings>>>Turn off International assist.