I changed my pickup time via the National call enter but that was not relayed to the rental location. When I arrived, I had to wait for two hours because the personnel at that location were getting a car fixed and manning a second location. When someone finally arrived to get me my car, they indicated the car I had reserved had been given to another customer as they had not received my new pick-up time from the National customer service call center. So I ended up driving a much smaller vehicle than I had reserved, which I received only after waiting two hours at the rental location, during which time the National customer service reps were of little help. Last time I rent from National if there is another option.