Update: I just heard back from AVIS and they have a record of someone else renting the car we had the same day we returned it. So, they should refund our money soon. I'm really glad I caught that charge, and relieved it was so easy to resolve!
We spent nearly a week in Florida a couple weeks ago. We had a rental car through AVIS for the whole time we were there. I returned it on time, even spent extra on a hotel that had a shuttle that would take me to the AUTEC terminal the next morning so I wouldn't have to keep it any extra time. Everything seemed fine, and I saw the guy who returned it check our odometer and tell me all was well.
Fast forward to this week, when I noticed a charge on our credit card account that was more than we'd initially paid for our rental (we booked it through Priceline, which is SO much cheaper than anything else we've tried) from AVIS. So, I sent an email disputing the charge. They came back and told me that we'd supposedly returned the car four days late, so we were being charged for the extra days plus late fees.
Wow. I was a little blown away by that. We've rented a lot of cars since we've moved here and this is the first problem we've had. The return was exactly like all the others, too. I don't really blame AVIS in particular since we've used them before with no ill effects, but clearly some paperwork was not done or filled out incorrectly. I'm waiting for them to get back to me about it, but we've been debating how to prove we returned it on time. We didn't fly commercially, so don't have a plane ticket to prove we left the area, but Oliver thinks he can get a letter from his command stating we returned the day we did. Clearly, we have no need of a rental if we weren't even in the country, right?
Anyway, just thought I'd pass this on with a tip - if you are renting a car, make sure they actually returned it for you. Otherwise, they will sock you with big charges. This is kind of aggravating, too, because car rental companies almost never give you anything when you return your car. They just look at the paperwork, check the odometer, and send you on your way. I guess I can't let that be it next time...