First question: I have a 4GB iPhone and I was thinking of getting a 8 or 16GB one, would I be able to trade in my iPhone for one of those and of course pay difference? I sure I won't be able to trade my 4GB for $300 because its been used but maybe around $250 or so? Second question: I keep getting this "error" that tells me that "This Accessory is Not Made to Work for iPhone" and asks if I want to enable Airport Mode. It comes up every time I unlock my phone, randomly when my phone is locked, when I plug my phone in to sync it or into my standard iPhone charger that I've used ever since I got my phone. I haven't done anything to my phone like getting it wet, unlocking it or dropping it. Thanks for any input!