New charges, desk staff not helpful

1) The online booking was fine. But when at the EZ/Easy/Advantage DESK to pick up the PREPAID car, they said I owed a further $27... could NOT say for what. I showed them my "fully paid, pay nothing at pickup" printed receipt from the online booking, but the desk clerk just kept exclaiming "it's on the screen!" and "that's another company (who books online), not Advantage, so that's their problem!". I paid the darn $27 to get the car, PLUS ANOTHER $200 "DEPOSIT" which I did not read about ANYWHERE when I was booking. Stressful pick up. But the good news is the car was fine, and the $227 charge has now disappeared off my credit card after returning the car. So the desk clerk really has no idea and could not explain any of that, which would have been much more helpful. 2) I had to electronically sign on their system that I accept their insurance, but I was DECLINING, as I have my own insurance (and for my own insurance to kick in, I MUST "decline" the rental insurance). The clerk kept saying "it's included!" Confusing, as the online booking did not include insurance and I was not being charged for it. If insurance is free/included, by all means say so all over the place!