Before pressing the Submit button, be sure your choices are correct. After you press Submit, you'll be taken to the payments page, and at that point there's no way to make changes to your selections.
If you discover a problem after pressing Submit, but before paying, you'll need to cancel out of the payment process, reload this page, and start over. You will not be charged unless you complete the payment process and receive a payment confirmation.
Sorry for any inconvenience.