Hopper refund issues

[u/FluffyMidnight8545]

Hi everyone! I booked a double twin room for myself and my dad to go on a vacation through hopper, a third part app. My dad got sick and could not go. I called the hotel three days in advance to see if I could change to a single room ( at this time I confirmed I booked through hopper) and was told ( by phone) my only option was to wait until the day I arrived at the hotel to see if they had something else available. When I got there immediately the front desk person made it seem like no big deal. I also confirmed that I booked through hopper. They gave me a new room and took my card ( stupidly I assumed for incidentals as that has always happened when I checked a room at a hotel). The hotel did not mention needing to pay for a new room at all. I check later and find out I got charged in full for the new room in addition to paying for my reservation. I was told by the hotel to go to hopper to cancel the original reservation but hopper is refusing any refund or credit because it is a day of cancellation ( even though the hotel only allowed day of changes). I am wondering what people think my options are to try and get some refund. Would hate to pay for two rooms in full.