应不应该付钱 ??

家里的水管没了热水，叫来Plumber，Plumber来了后，看了半分钟，said hot water should be in left side, not in right side. (be fair, it was some kind stupid mistake we made), anyway, that was it (we used wrong side of handler). He charged us $105 for this. I thought it was not reasonable for this, I offered $50 for him, but he didn't take instead he threatened us to go to the court.

What do your guys think? Should I pay full amount or just ignore???

Thanks in advance.