If a shop displays a sign saying "blackberry unlocking £15", does that mean they unlock them from contract to pay as you go or does it mean they unlock it from one network to another?.
If you unlock your phone using the unlock code , your phone gets permanently unlocked. It will not ask for any other unlock code in the future. After you unlock your phone, you can use it with any other network's sim card.
And its not necessary to take it to a service provider you can get codes and unlock yourself.Try this site The Unlock Arena - ---