I rented a car on the 15 of December 2024 at the Nelspruit branch under unlimited kilometers for three days

I rented a car on the 15 of December 2024 at the Nelspruit branch under unlimited kilometers for three days. I returned on the 17th of December 2024. According to my understanding, the car was returned before the expiry of three days.Hertz rental car charged me per kilometer, which is more than what we agreed on or different compared to the contract I signed. Up to now, they do not want to return my money. Kind regards LS Khoza