I have sent an email to the rental company addressing the issues.

Since we arrived in Frankfurt on an early flight, there were two groups before us, and we waited for a while. I had booked a seven-seater car. The customer service offered us a five-seater Volvo going back to Zurich with a 450 Euro one-way rental fee if we were willing. Considering our comfort, we decided to stick with the seven-seater we originally booked.

There has been no follow-up after requesting the charge details and reasons, even after providing photo evidence. This is quite disappointing.

Efficient but the reserved model was not available, had to upgrade to automatic for an extra fee

I rented the car at Frankfurt Airport. The rental station was large and well-organized, with all the major companies together. Car rentals are very developed here.