"Your most unhappy customers are your greatest source of learning!"
Instead of dodging the next upset client you have to deal with, how about directly addressing the problem? How about instead of looking at Caller ID and deciding you don't want to talk to them, you answer the phone on the first ring and simply be upbeat. Plus, if you smile as you're talking, it'll come through in the tone of your voice.
An angry customer, depending on your approach, can do almost as much to help your business as a satisfied client. In fact, some times the relationship will get even stronger. Why? Because they recognize you're standing behind your product; that you're passionate and you believe in your skill set as an artist. An upset customer, even if you did absolutely nothing wrong, is an opportunity for you to demonstrate your ability to empathize and your integrity.
A lot of business owners have a hard time getting started. Here's the easiest one liner on the planet to help you diffuse an upset client:
"I understand you're unhappy. Well, the buck stops here. What can I do to help?" Then, just kick back and listen.
What you don't want to do is ignore their issue, because it'll only get worse. In addition, be careful talking about the challenge in any of the Facebook forums. I'm amazed at photographers who shred a client in a public forum, when there's a distinct possibility it's going to get back to them. Whether the customer was wrong or not doesn't make any difference. That customer who's being bashed is one of the bricks in the foundation of your business. Why not recognize his/her value and solve the problem instead of treating them like they were disposable?
It's another old quote, but so appropriate to wrap up this topic:
He is not dependent on us. We are dependent on him.
He is not an interruption in our work. He is the purpose of it.
He is not an outsider in our business. He is part of it.
We are not doing him a favor by serving him. He is doing us a favor by giving us an opportunity to do so.”