Got overcharged $300 at Horseshoe vegas - they claim I didn't reserve with rewards!

I recently completed a 4-night stay at Caesars Horseshoe Hotel on the Las Vegas strip. I used my Caesars Rewards app to make the booking (I've had the same account for years). I was supposed to get two nights free and the other two nights were showing low rates (for a grand total of $627 including resort fees/taxes).

After checking out, I looked at the folio and the total was $925 ($298) higher than expected. I called Horseshoe and they claim that I got the rate that I booked, and I didn't use my rewards to book/I booked online. All of this is false. I had a screenshot of the guaranteed rate right before I pressed "book" on the app. Nothing that I was guaranteed lines up with what they charged me. I escalated with them and the person still said everything went thru normally and that I didn't use my rewards or app. I can literally see the rewards number in my receipt and everything was done on the app.

Has anyone had an issue with this? I am planning to dispute it with the bank.