Reduced reservation by one day and charged ~$100 more

I had a seven day reservation which I reduced to six at about the fifth day. I was hoping for partial refund or at least to let the place be available for others. I misread it as saying ~$100 refund when it was actually me being charged $100 more. Of course, I should have read more closely before requesting this, but I am feeling cheated for getting charged more for less. Spent over an hour with airbnb support only to be told that it's policy not to change this. The host first insisted this was a fee from airbnb and not going to them and then later acknowledged the issue but said tough. Planning to leave a very negative review and avoid airbnb as much as possible in the future. Anything else to be done?