First you should check with your consumer protection laws, where I am from (Brazil) any cancelation fee that is more than 10% of the service value is considered

First you should check with your consumer protection laws, where I am from (Brazil) any cancelation fee that is more than 10% of the service value is considered abusive. So you are totally entitled to ask for your chargeback (just be sure to cite the regulation/law your applying) and if AirBnb does any retaliation (as banning your account) you can sue them for that.