I've never flown EasyJet but I did try renting a car from Easycar when I was in AMS. We made online reservations and showed up at the rental location (not the airport one, one outside of town - figured it'd be easier to take the train out of the city and pick up the car there than try to navigate in AMS). They didn't have ANY cars left and said we could come back the next day or go to the airport location and pick one up. We decided against getting the car as we were only going to do a day trip out in the country side. It took us about 3 hours and several long distance calls to England to get our money refunded. I DO NOT RECOMMEND EASY CAR!! It was the biggest hassle ever. Wasted an entire day with that!