I just sold my 3gs to someone to buy the iPhone 4...I erased all of my data and took out my sim card...however when he got to my apartment, he wanted to verify it could make a call. I put in my sim and connected to itunes (just letting it register and not setting it up as either a new phone or restoring from a backup). He made a call and I took out the sim and sold it to him. However I'm a little worried that the phone is now still activated on my account...is it...or does it need my sim for that? Is there anything I need to do to make sure the new owner doesn't incur charges on my account? Thanks! Mark.