I don't have a SIM for my iPhone 4 and was using it as an iPod. I decided to update it and now it won't activate, I know there are some tethered hacks but my husband says I won't have any of the features I want. I also read that using an AT&T SIM would allow me to activate it. What I'm wondering is if the card actually has to be activated, or can I get a used one on eBay? Please help me out. Been sear hint for hours if not days for this answer!