My dad is happy with his iphone and has been given the new iphone 4 however he still likes his 3GS (dont ask) anyways, i am on o2 so i have gave him £200 for the iphone 4 and have spoke to 02 and there sending me out a sim for it, however can i put the o2 sim in the vodafone iphone 4 or not? do i need an unlocking code? please help thank you.