I booked a rental car through one of these broker platforms at Keddy at Frankfurt Airport. The person at the Europcar counter was aggressive and unfriendly. I can stand the usual attempts to push you into a more expensive rental, but this went far beyond: no car before the printed rental time - I had to wait 12 min. At rental time, no car was in the booked category, and the reservation was at the other terminal (which was a lie), so I had to wait by the counter for another 9 minutes. Finally, I got a car key, but it was unclear which floor or parking spot to find the car. So, I went back to the counter. My comment that I was tired from the flight and trying to rent a car for more than one hour was the tipping point. The guy lost his temper, pointing fingers and shouting at me... I have been waiting for a response from the customer care center for two weeks... Thanks, but I will, and you shouldn't use this service!