I once picked up my phone at work to find Kate Adie (BBC war reporter) on the other end. I have a fairly uncommon name, but there were two of us at work, and she was put through to the wrong one.
She didn't pause for breath before berating "me" about some issue with her book, and so when I pointed out she had the wrong publisher she was already in rant mode. It was, it seemed to me, a really small issue, but she was incandescent, and didn't apologise for being foul to the wrong person.
I pitied her publisher, and immediately stopped complaining in my head about my authors who were often a bit difficult.
Again, it could've been a final straw, but it really knocked the wind out of me!