I live in China and I recently bought a refurbished iPhone 3GS from the US. It was jailbroken when I bought it and I personally prefer it un-jailbroken. Well, I contacted AT&T to see if I could get it unlocked and they agreed and told me to restore it. I restored it from a copy of the current iOS (unaltered) that I have saved to my computer. Well, I can't get it to activate because it says there is no SIM card installed or that the Activation Servers are down. I've previously unlocked an iPhone this way for a friend and had no problems. So, my question is do I need to restore and download a new copy of the iOS (I didn't think I needed to as I thought the activation server would take care of the unlock) or is there some other problem that I have overlooked?