10 or 15 years ago I'd be very confident that it would have been dealt with promptly at check-in. This is what it was like when we stayed on BRG in a Marriott Residence Inn in CA somewhere. We got to the front desk and was about the sign the paper. The paper said $132 vs $89 (I know the difference is not huge, but still). I showed the front desk my original reservation and they still couldn't figure it out and after 15 minutes also our rate was honoured and checked in as usual.

I think if the hotel refuses nowadays and the GM doesn't budge you are basically SOL. If you try to dispute it with your CC issuer you might get your account blocked.