CC fraud policy question

I need to write a policy regarding refunds for disputed credit card transactions, namely that we don't give them. Does anyone have a sample to share?

We had a customer dispute a charge, where the card was present and swiped at the window. We do not currently require a signature or id to charge a card. The cc company told the patron they had to take it up with us, and in the name of customer service, our Box Office Manager refunded the card, even though it was a card present transaction, and the tickets purchased were already used.

I would like to avoid this situation in the future. Thanks!