In the past, in the few weeks between selling my current iPhone and getting the new one, I'd just use my original iPhone in the interim (with the help of a microsim adapter obviously once I went to the 4). I hope to do this again this year - but- I can't seem to find it right now, but I could have sworn I read something earlier in the year or maybe late last year about AT&T not letting that happen any longer. It was something about they charged you some fee automatically if you did that, or screwed with your data plan or some such. Can anybody confirm/deny? OR - if not, if I take my original iPhone to ATT will they supply me with a full-size SIM to pop in and go? Will my unlimited data plan remain unchanged?