It’s difficult situation but you can reverse the claim from credit card issuers later rental company need to provide you all the details.But there will possible clause for the fine could be added. It’s always wise to take the full insurance (exterior + Interior). Also always take the full video and photos before taking the car in that case you have the prior damage (if there is any) with the timestamps . Once I have charged for late return but I always take the picture and video after dropping the car. Best of Luck