Ok, ... in which case buy a cheap unlocked PAYG phone and put your sim straight in keeping your same number ... about 2x weeks before your contract is up ask for your PAC (porting authorisation code) from O2 and then within 1 month get new contract with someone else giving them you PAC ... this means you get to keep your number even if you go to Orange / Voda ? Tmob or Virgin ... Just dont go to 3 ! Plus, asking for your PAC generally makes companies give you a better phone on an upgrade than you would have got before !! Good luck ...