I've got an old iPhone 4 that I don't use anymore, and am considering trying to sell it or something. However, I have erased it, and I cannot activate it, as it requires a SIM card that is on the network that I used to be with when I first got the phone. I was with EE, and am now with Three. Is there any way I can get the iPhone unlocked, or do I need to find a friend who has an EE SIM card, and THEN unlock it?