Really Annoying Man..

I love my job and the people that work there and the customers..most of the time.  Every once in a while though,  we get a customer who complains about every little thing. Then we get customers who are too stupid to work a lamp light(this really did happen).  Recently though, I had a customer who wanted details about every single thing on the hotel.  I have never had a customer like this.  This customer wanted to know details on the Internet, who we went through, was it DSL or cable, where each antenna was exactly, then he moved to the breakfast bar.  I told him everything about it, right down to our sugar packets. By the way our breakfast bar has a lot of stuff so this took several minutes.  I finally realized that no matter what I told this customer that his reservation was already paid for.  I started getting suspicious.  I thought, "This man wants to know all these details so if one tiny thing is wrong he can complain about it and get a discount."  Sure enough that's exactly what he did.   I really hate dishonest people. It just makes me so angry how customers take advantage of businesses.  Maybe this could be the irritability that you get during pregnancy, but I am really starting to get annoyed with some of these dishonest customers. Fortunately when I do get irritated by them I go into "Barbie Happy Mode". Meaning my voice gets higher, I have a perkiness to it. I also just can't keep smiling and moving my hand like the flight attendants, showing idiots how to buckle their seat belts.  Only my coworkers can tell when I am in that mode.  They think it's hilarious because while the customer thinks I am being super nice and perky secretly I want to reach over and grab their nose(a customer did this to me, so creepy).So I am wondering has this ever happen to you?  Have you almost lost your cool with a customer?