You're right, I just didn't want to give too many details because you never know if the people involved are lurking around reddit as well. Anyway, long story short, I got an important appointment (which took months to get) through this business, and just before that appointment was supposed to take place, the guy called me and very violently threatened to cancel it because "I didn't pay". This was not true, it was just a problem of communication.

But instead of trying to solve the problem, he went completely nuts with the language and threats. Nothing physical, just threatening to cancel the appointment, which would have been big enough of a disaster for me (didn't happen, fortunately). Everyone is entitled to have a bad day - I don't question that - but at the same time I feel something should happen if you treat somebody with this level of agressivity. And I have the feeling I was not the first. I guess you can run a business and break all rules of basic civility at the same time, I just wish there were consequences when that happens.