I'm sure some of the stories are embellished, but no doubt some are true. I worked in customer service type jobs for years myself and have been absolutely stunned by some customers' behavior. One memorable encounter when I was a teenager - I was working at a local BBQ restaurant. It had a set up similiar to Sonic where people could pull up to individual electronic menus and order a meal to be delivered to their car (no roller skates though!). One night close to closing time, someone pulled up and ordered a meal and a "large orange drink". The lady taking the order told them we didn't have orange drink. "OK, a small orange drink". Sorry, no orange drink at all. Then they ordered another odd drink we didn't have and did the same thing...changed the size but not the drink itself. It was odd, but I thought maybe they were trying to be funny. We finally got their order after much back and forth. It was my turn to deliver the meal, turns out it was an older couple. They insisted I wait while they checked their order (no big deal there), but then when they decided it was wrong. They insisted they ordered something we didn't even have on our menu, and the man started screaming and cursing me out. I tried to explain we didn't even serve that item, and the lady starts screaming "Shut up! Shut up!". The man says "Are you talking to me or her?" The lady says "HER!" It was truly crazy. They then threw their money at me, followed by a bunch of trash from their car. I was so mad I was shaking, my manager let me go home immediately.
I also worked in a call center for an insurance company, and got cursed out on a regular basis there. I could kind of understand people being upset when a claim was denied or something like that, but people would get angry over the craziest things. For example, we had a deal with a grocery store chain where everybody in the state with one of their loyalty cards got a free $1000 accidental death policy. They could purchase extra if they wanted, but the $1000 policy was at absolutely no cost and they didn't even have to do anything. I had more than one person call and yell at me about it. I couldn't even figure out exactly why they were so mad, maybe they just didn't like getting mail?