I did exactly that, went into the ATT store to pay the one remaining payment. I couldn't do it because it is tied into trading the phone on the spot. So I too have one payment remaining which they have told me can be paid off at the time I pre-order! I believe, but don't know this for a fact, that you can initiate your pre-order through Apple but they make you go to the ATT website to make the balance payment. That's why Apple is now requiring that you have the special ATT password because I think it's all tied together. Don't quote me though, just that I tried a pretend upgrade through Apple last week and that's what it looked like.