Story time.
It's Halloween, so let me tell you a bit of a customer service horror story from back when I was working as a cashier at a grocery store a few months ago:

It's approaching noon on a weekday, which usually means that things will start to finally get busy in comparison to the usual morning customers which consisted of people buying coffee and newspapers. I was new and working in the express lane, so the sudden influx of customers meant that a large number of them would be going through my line. Two customers came up, a pair yet paying separately. They were both older Hispanic women, buying a few normal items each. The first one went just fine. I was polite, bagged her stuff, and when she paid and was given her receipt, she stood over to wait while I processed her friend. The second woman seemed to go along normally, right up until she had to pay. The order was only for a bit under $10, and I guess the lady works as a coffee machine part-time, because she started trying to pay me in chunks of quarters.

Let me restate this: It's busy. I have about five people in my line, and a woman is trying to pay for her items by slowly counting out quarters and handing them to me. She would reach into her purse, slowly but surely fishing out a collection of four quarters to drop into my waiting, cupped hand. "One dollar..." More fishing around, and another small stack of clanging metal coins. "Two dollar..." I looked back at the customers who were patiently waiting as this play of sheer ridiculousness was going on before me, and I was an involuntary part of it. The folks kindly waiting managed to chuckle and smirk at me as I looked at them with a pleading face, their humored support resting my mind that one of them won't start screaming out of frustration. They understand, I thought to myself. There's absolutely nothing I can do besides stand here and wait. Slowly and surely, the older woman demonstrates her ability to count out quarters. "Seven dollar..." I start to smirk. I can't help it. My glances over to those waiting in line, and their amusement is contagious. I try my best to hold myself back. "Eight dollar..."

I snerk. Not a chuckle, mind you. More like air escaping my nose as I hold back laughter.
She looks up at me and asks, "What's wrong with you?"
"What?"
"I hand you money and you laugh at me! What is wrong with you!?"
Oh shit. "N-no, I'm sorry. I wasn't... it was about something else." I was caught off guard. So sue me that I wasn't able to come up with something good on the fly.
The women continues to try and find out what exactly was was wrong with me, seeing past my pathetic lie. I desperately try damage control while she finally picks up the pace, handing me the last two stacks of quarters. I quickly process her, hand her receipt and change, and send her and her friend along the way. I should have apologized again, but at that point I just wanted her out of there lest a manager walk by and the woman gets the idea to complain about me. As she walks out the door and I process the man who had been waiting in line, the old woman looks back towards me and says, "I'm never shopping here again."
I look back and say, "O.K."

Bad service and control on my part, yes, but honestly? What would you have done?