From my experience with Hertz at the DEN airport is that the attendants have been fairly dense and they don't listen to what you request. "Oh you want to change

From my experience with Hertz at the DEN airport is that the attendants have been fairly dense and they don't listen to what you request. "Oh you want to change the credit card on the reservation" ... later when questioned "oh i would have to cancel the reservation and rebook it to do that" It hasn't happened just once.