Our customer went to buy an airline ticket on his debit card and they told him it was denied. He then gave them a credit card to complete the transaction. Later, he saw it memo posted and called the airline. Instead of reversing it, they told him that the bank would have to correct it for him. What MasteCard chargeback code should we use? Duplicate Transaction doesn't sound like it qualifies. How about Duplicate Processing (4834)?

Since the charge was not processed twice on the debit card, 4834 would not be appropriate. Use code 4831 "Transaction Amount Differs" as one of the proper uses for this code is "payment by other means." See Section 3.15.4 of the MasterCard Chargeback Guide May 23, 2012 edition. To aid in the investigation, ask the customer to provide a statement from their credit card showing that the charge was also processed on that card. Also, ask the cardholder to write a letter stating that the charge on the credit card is for the same services as what was charged on the debit card.

Thanks Brian! I was trying to look through the guide, but I keep getting interrupted by auditors wanting things, so I haven't been able to look through a lot of the guide.