We stopped using Blockbuster years ago for a similar reason...
I returned two movies to their night drop box; a month later, we got a letter in the mail saying that we didn't return one of the two movies and that they were going to bill us $80.00 for it! WTF?!? We called them on the phone and told them we returned both at the same time and that they must have just misplaced it incorrectly logged it or something. They basically told us "too bad, here's a bill for $80 bucks".
In a fit of intense rage, I went over to the actual Blockbuster store and took up the issue with the pimply-faced manager. I cursed his azz upside down and backwards, disparaging his entire family lineage in the process. Other patrons started starring, and as I intensified my actions they just left the store, taking their children with them, who probably shouldn't hear the kind of colorful language I was spewing. Eventually they called the cops (I think it was after about the 30th "motherf***er" I dropped) and I figured I'd finally gotten my $80 worth of enternainment out of the deal.
I smiled, waved, and walked out saying, "have a nice f***ing day!" :waving: