I have a virigin un-jailbroken iphone on at&t and am planning to sell it in a while so i can upgrade to the next iphone.. ive discovered that iphones that are unlocked are going for a higher price than those that aren't. So if i posted saying i could unlock it can i just take out my sim, restore it, run the ziphone unlock setting, and then put whoever buys my phone sim in it and they'd be up and running??? do i need a sim in the phone as i run ziphone? thanks