They won't bill you until the phone is shipped, which going off previous releases could be as early as Sunday. Once your order changes to "processing" you should be able to edit the billing information. As for my orders. I got the confirmation for my girlfriend's iPhone at 3:24am est. and hers is now processing. I got the confirmation for mine at 3:30am est. and it is still in the "received order" phase. It should switch anytime now. Both are still showing delivery dates for 9/21.
mine says del Oct 5, my card has been charged since the 14th