After what you have already read about Greenmotion, I suppose nothing can or will shock you any further. My story is surprisingly mild in comparison to those others I have read. Mine ended up costing me ´´just´´´500 EUR, and in accordance with their T&C's they were legally obliged to take those 500 EUR. I rented a car at their Warsaw Airport office, upon receiving the car I asked the clerk if I should be aware of any cross border fee as I was taking the car 20 kilometers into Czech republic. The guy said they I'll pay 100 EUR upon return of the vehicle for crossing a border. I thought that was super expensive, but having not other choice I went with it. Upon returning the car, they surprisingly agreed that I had no damages done to the car. I expected them to take 100 EUR of my 700 EUR deposit, but no. They took 500 EUR for an unauthorized border crossing. It was in the T&C, but I wrongfully trusted their clerk.. So yes expensive learning experience. Dont use them, ever. You will get screw in one way or another.