Answer:
You are required to take care of your customer. You can ask if they have tried to work it out with the merchant, but you can't require it. The purpose of this is that you and the merchant both don't debit the account.
Section 1005.6 and Section 1005.11 both indicate you have received an error when the consumer informs you. These sections also require you to investigate promptly.
First published on BankersOnline.com 6/20/11; Regulation links updated 12/31/12