I understand your thoughts. But. Number one. 40 bucks is cheap. My charge would have been 120. Second. This guy is a jerk. No matter what. You did absolutely nothing wrong. Nothing at all. Zippo. And the minute you start letting the customers run you and your business, you'd better just close up shop, cause you just drew a line in the sand that says, "run me over". Standing your ground, taking payment was the only thing to do. But I am more concerned with the fact your asking a question about whether it was right or not. Please read on.
About him telling his freinds. Think about this. Birds of a feather flock together. His freinds are a-holes too. So those customers are not needed in a moving forward business.
I want to pick on you for a second. I mean this with all the respect in the world. So please, if it doesn't sound respectable, just know that it's not meant to hurt you.
Here is an example of our industries troubles. We are allowing the respect of what we do, what were about, how we conduct ourselves to be driven solely by what the customer's actions seem to be. We collectively are bending over and being too accomadating to the general public at large. The fact you had to ask this question, and many questions like this that come up on here, tells me, that our heads are not screwed on straight and the owners and techs need some reality based dollars and sense and business classes.
Example. Your cell phone. Whatever company. It has it's charges. It's rules of engagement. You make the calls and your time is tallied and then your billed. Unless of a unique circumstance, you have to pay the bill, or they cancel you, then your blacklisted also. They look at you as a bad customer, and they can not dick around with you. They focus in on who pays the bills and leave you hanging.
Tell me why on earth we don't conduct ourselves the same way. I can tell you from my own hard knocks of learning this gem of leadership in my own small business. I never once lost out when I have fired customers from my business. It just has to be done. You can't fret over it. You just move on. Recently I had to make a very painful decision about a customer who was a large dollar amount to my business but has experienced bad times and their ability to pay has diminished. I have great relationships with the people at this account. And they were a little dismayed that I am unwilling to wait for their money any longer.
Bottom line. I am like the cell phone company. I need paying customers. I run a business.
Additionally, the lack of respect some customers display, that alone tells me that they don't pay well, so stay away from those types. And even if those types do pay well, you'll fight for ever dollar. That takes time most people don't have. It's not worth putting up with.