Hyatt regency incline village Lake Tahoe Nevada Over charge Incline village Nevada

I rented a king room in the hotel for November 23 to 25 th. I changed my reservation to a double bed cottage room for $545.76. Per night. I received an upgrade add for a one bedroom beach cottage for $100 extra per night. I excepted that offer. No other email confirmations were sent me other than these three.
Hyatt says I was offered a 1 bedroom cottage non beach access for 600 a night. That I accepted that and then accepted the beach access for 100 more a night. I never accepted or saw a 600$ upgrade. I have asked them to provide that to me as they immediately sent me email confirmation every time . They just said nope. No refund.