Sixt Charged More Than Agreed for Car Rental

I rented a car from Sixt in Düsseldorf, Germany, with reservation number 9935943389. When I went to pick up the car, I was asked to pay more than the initially agreed amount. Despite this unexpected increase, I accepted and proceeded with the rental. However, after returning the car, I noticed that I was charged even more than the amount we had discussed at the counter.

I have reached out to Sixt through multiple written communications, but I have not received any response regarding this overcharge. I need Sixt to address this issue promptly and refund the extra amount that was wrongly charged. This lack of communication and resolution is very frustrating, and I expect a timely response.