(I work at a major big box home improvement store where we have a garden center outside where I was running the register this day)
Customer: All I see here are your outdoor plants. Where do you keep your indoor plants?
Me: Ummm…that would be right inside. *facepalm*

(I work for a counter fraud department within a large well known insurance company, primarily my job consists of investigating new policies and looking for any signs that might link to fraud, fraud rings, ghostbrokers etc and validating the information on new policies, however sometimes we do take an occasional call from a policy holder who’s file we investigated)

Caller: Hi, my policy was cancelled by you and my new insurer is looking for proof of no claims, I should have 11 years?

Me: Alright let me have a look for you.

(I check his file and notice we confirmed with his last insurer  that he left them with 9 years and was with us for a year so he is entitled to 10)

Me: Okay sir, I can send you an email confirming 10 years no claims discount is that okay?

Caller: No I have 11! I had 9 with [Last insurers name] and have been with you for a whole year so 11!

Me: No sir that would be 10 years no claims discount…

Caller: *In an belittling tone* Please explain to me how you are coming up with this calculation because I did the maths and you owe me 11 years no claims discount!

Me: Certainly sir, well 1 + 1 is 2 yes?

Caller: Yes..

Me: And when you add 1 to another number that number becomes 1 more than it already is yes?

Caller: Yes?…

Me: Therefore 9 + 1 is 10, I’ll send out the email within the next 24hrs.

Caller: Oh, okay.. Uhm.. *Click*

This happened during my last month at my old part-time job. I was at the register, when two customers (a man and his wife) drove up to pump gas. As they got out, I noticed that they were smoking and not putting it out.

Me: Excuse me. I need you two to put those out before you start.

They both acknowledged what I just said. A few minutes later, I had just finished with another customer, when I noticed that the wife was still smoking.

Me: Ma’am. I need you to put that cigarette out. It’s a fire hazard.

She looked at me, apparently having heard what I said, so I went back to my register. A few minutes later, I saw that she was STILL smoking.

Me: Ma’am. This is the third time I’ve had to tell you. You can’t smoke here. It’s a fire hazard.

Finally, she takes out her cigarette and (without looking down to make sure there wasn’t any oil or something) throws it on the ground. She kinda scowled at me the rest of the time she was there. Her husband kept giving me an apologetic look.

(Note the customer was being incredibly annoying and rude, and all she ordered was a child’s ice cream cone, and we usually give extra swirls on it, just to be nice, but I gave her the right amount which is only two swirls when we usually do 1 or two extra.)
Customer: This is way smaller than a child’s cone! I want a refund and for you to make me a new one! *She keeps rambling on and starts to yell, the manager comes over and she shows him the cone with a smirk.*
Manager: Ma’am this is the correct size. I would ask you to stop harassing my employees and holding up the line, before you get banned.
(She yells one final “F*** you”, and drives away)

(I work in a relatively popular restaurant in a wealthy neighborhood, and have for 8 years. This evening we are quite busy with large groups – 6 or more people. A group of 11 ladies with no reservation come in and decide to sit outside on our covered terrace. We have a smoking bar next to the terrace which guests are informed of before they sit. One of the ladies waves me over.)

Customer: Miss, we were told this patio was non-smoking, but we smell smoke.

Me: I am sorry ladies. Yes, the patio is non-smoking, however there is a smoking bar nearby.

Customer: They said smokers have to go over there (she points to a bench out of the way).

Me: I am terribly sorry you were misinformed, ladies, but yes. The smoking bar is open tonight. Our apologies for the confusion.

(At this point, I go to head to my section as this is not my table and I overhear the woman say:)

Customer: Well, like YOU care, anyway.

(For whatever reason, this hit me the wrong way. Maybe it was because I had been working 12 hours already and it was humid as heck.)

Me: Ma’am, I DO care about my customers. Very much. Always do. But you were informed of the smoking bar. And I can’t move it for you.

(I walked away at this point. The manager came over and explained again that there was no other place for them to move to. The ladies tried to convince the manager to move the tables to a different spot on the patio, which was not going to happen.)