so ive just bought the iPhone 4 second hand, the guy reset the phone so it was like brand new! I'm now at home and can not get past the activation screen, as i was told it was unlocked and it must not be! ive tried with sim card and without! i get these messages 'Activation request could not be completed, if the problem persists, please contact customer care' or 'Only compatible SIM cards from a supported carrier may be used to activate iPhone. Please insert the SIM card that came with your iPhone or vist a supported carrier's store to receive a replacement SIM card' someone please help?