I only mentioned that your incident was definitely an exception, so I would think twice, to avoid Sixt in the future due to the (nearly overall) great service, cars (and rates if your credit card covers the CDW).

The only situation I can remember was an offered (!) additional charge of 15 EUR at STR because of my premature arrival in the Sixt station at 11.20 a.m., having a weekend-reservation, which starts regularly at noon.

Had a coffee instead, came back at 11.45 and got a MB CLS for my LDAR reservation. Who cares, thanks.

Never had any problems like this ridiculous one ever.