Yeah, you definitely need to get it sorted out with Avis. While we understand why you'd want to pursue a credit card chargeback, just keep in mind that this could land you on the Do Not Rent list which means you may never be able to rent from Avis/Budget/Payless in the future. Even if you are in the right, once you are put on the list, it can be very hard to get off.

You might want to try escalating with some of the contacts on this page.