Sandos Caracol Eco Resort review: Double charged me for my room and not issuing a refund

I stayed at Sandos Caracol for 8 days in April with a hotel charge of about $2,000. At the beginning of the stay I was asked for my credit card. At the end of the stay, when we checked out, I was asked for a credit card AGAIN which I thought was to process the final bill. Unintentionally, I provided a different card the second time (both are Visa). As I found out months later, I was charged on both credit cards for the entire stay. I didn't catch this because I was doing a lot of remodeling at the time so I had expected my credit use to be higher than normal during that period. Furthermore, I only saw the one charge and didn't compare the cards side-by-side until I was

To their credit, a Sandos manager sent an email acknowledging their mistake a week after I returned. However, gmail treated an unsolicited email from Mexico as spam. I did not see the email until I did a search several months later. By the time I called my credit card company to dispute the bill, it was past the 60 day period. I contacted Sandos at the same time and asked them to process the refund. I have provided all the information they required and I'm told they can't do it because their system won't allow it.