I just hab a terrible experience from Avis in Orlando, their customer service is a joke and is no help at all, they can't authorize any credit and won't let you talk to anyone who can.
I had a confirmed rate for a rental on a multiple week rental but was forced to return it a couple of days early due to a family emergency, by doing this I found out that I voided the rate and they can charge any new rate they want, which resulted in $500 additional charges. I did not want any special treatment or expect a reduced charge for a shorter rental, I just wanted to pay the charge I was quoted, Avis just wanted to find a reason to charge more.