Sorry, but my situation has nothing to do with the "tariff". It has to do with getting frequent rental points credited to the program of my choice - SPG. I have had to repeatedly request credit for these points over the last 2 years. I have much e-mail correspondence with Sixt representatives that document that there is a problem with the Sixt system.

You're talking about tariffs, I'm talking about credit for rentals. Apples & Oranges.