Courtyard by Marriott Dayton University of Dayton review: Over charging for room rental for 3 nights

We stayed at this hotel for 3 nights on june 23,24,25th of 2022. We were to receive a special convention rate of $99.00 a night plus tax. They charged me $199.00 plus tax. They issued a refund to me on my credit card od $300. which I was ok with. The credit card company viewed at a chargeof $300. which means They owe me now$600.

I have contacted the credit card company 3 times and each time they said they would send me the paperwork to correct the error,. I have received nothing from them to date. This stared early in August.

I have an email from the courtyard showing the credit of $300.

What do I have to do to clear this up with Visa and the Sentry Credit Union.

I will never pay the $600. and will cancel the card if they try to collect or I will have to get an attorney to help me. Lyall Schroeder