Actually is happening to me, too. I talked with Apple on the site Sunday and they said pretty much what everyone else has been saying: they're deploying a fix for it and will stay in contact with me as it goes through. Checked this morning, my grand total is still at around $951 on what was originally just $84 in tax + upgrade fee (I have the exact same order as you, too: Plus, 64GB, Next 12).
Was freaking out a bit over the weekend even though I know I wouldn't be charged for another week and a half.