i recently got two phone lines on at&t one line has an iphone 4s and one line has the iphone 5. im using the line with the iphone 5 and no one is using the other line or 4s so my question is. can i sell my iphone 4s to my friend? would taking my sim card out of the 4s and my friend putting her 3gs sim card in there work? and we both have at&t.