I ran into a Hertz rate problem when traveling last month. Weeks ahead of time I'd arranged rental on a compact car, and when I stopped at the rental desk, all was still going as planned. But when I went out to get the car, it was "gone". They instead gave me a Jeep, for the same rate, they said. But when I returned the car the next day, they tried to charge me the Jeep rate. I eventually paid less, but not as little as promised, so I had to complain through customer service to get my refund. I'm not sure whether this happens regularly.