Bought a V3 from Tesco, got it unlocked to use on o2. So far so good. But when I pressed and held key "1" for the first time, it asked me if I wanted to assign a voicemail number. I did - and put in the wrong one. Now there seems no way to overwrite it. Even saving a new entry to the same position doesn't touch it. Anyone know how I can make it dial the right voicemail number (901)?