Just click on change payment link, if it take you straight to the last part of check out. It should take you back to the page where you can uncheck the credit. Which is the select payment section.
Order mine Sunday night, sent them an email to try and get the Disney coupon added. They best they could do for me is refund me $10, With the $10 promotion they have, I guess it end up being the same. Which is better than nothing.