Sure the network can do it J sure its around £15

They are locked end of, i had one on orange, i had to jailbreak it to get on o2 (then sold as unlocked) but could not use i tunes after the jailbreak.
They are locked & thats it end of unless you got that contract Jailbreak is the only way. Beware of what they will say is offical when its not, through using a false contract and it will work for so long then get blocked completely . Just use a good Jailbreak on it or keep it as it is