Ive tried searching but cant find anything although this has probably been answere before. Ive jailbroken the iphone but its still locked to o2, i cant use another sim, please help
you need to differentiate between unlocking the iphone and jail breaking. if you only jailed broken the iphone then it is still locked and you need to unlock it.
What you need to do is to restore the phone to an unactivated state before running QuickPwn. Put it into DFU mode (click here to see how) and restore to 2.2.1. This removes the current O2 activation. Do not activate in iTunes. Now run the QuickPwn process, and it will unlock it and let you use another carrier.