I wouldn't take it to the local market straight away as it is not the same as unlocking. You need the software reflashing or what we call "debranding" should cost about �10-�15. It is not easy as you must have the correct flash file and a programme called SE Tool. I used to do them in my shop and we always did it with a sense of trepidation as it can v easily go wrong. If you can not find a local independent who can do it for you I have a contact I could give you. PS it voids your warranty. And if it goes wrong your phone becomes an expensive paper weight.