Yeah, I'm adding Budget to my "do not rent" list. I just got billed $20/day for an "upgrade" at MCO. It was actually an involuntary upgrade, as they were out of the car class I had reserved, but yes, if you look at the fine print on the contract, it does indicate the upgrade fee and I did sign it. In my defense, it was after midnight after several hours of flight delays and I was in a rush; and of course, the agent said nothing about an upgrade fee, only that she was upgrading me due to a not having the car I reserved. It also took forever to check out because apparently un-picked-up rentals are purged from their system at midnight and have to be manually rebooked.

I did query customer service, but got the you signed it, you pay for it response.