Boilerplate Language for Bank Disputes?

Hello Hive Mind. 

We have been dealing with a large amount of fraudulent credit card activity though our website. In effort to combat some of the chargebacks that would have come from those charges, we went ahead and refunded any order that was flagged for having used a fraudulent card. However, for several of the orders that were refunded; the tickets were sold on a 3rd party website who showed up with the refunded tickets night of show. As a rule we make the patrons purchase new tickets if they still want to attend( as I am sure everyone else here does). We are now getting requests from those patrons requesting a letter to send to their bank to assist in their dispute for the original purchase through the third party. Does anyone have boiler plate language that they provide to patrons in this situation?