I've just spent over half an hour on a call with a woman who had a hospital claim declined, because she was not covered for that type of surgery on her policy.
Obviously, she is not happy.

Stupid Customer - "What's your telephone extension number? I am going to lodge such a huge complaint against you that you won't know what hit you!"

Me - "Okay. Well we don't actually have telephone extension numbers. We are identified by our Agent ID number. My Agent ID number is 4207"

Stupid Customer - "I TOLD you to give me my telephone extension number! You can't withold that information from you just to avoid getting the biggest complaint you're ever receive made against you!!"

Me - "Of course not ma'am. However, there are literally no telephone extension numbers within our company. They do not exist. I am ID'd by the Agent ID number 4207"

Stupid Customer - "GIVE ME YOUR TELEPHONE EXTENSION NUMBER YOU B*TCH!"

Me - "I can't give you what doesn't exist ma'am"

Stupid Customer - "I don't care! Make one up!"

Me - "Um... well, I imagine that would defeat the purpose ma'am. If I made up a telephone extension number and you use dit in a complaint against me, no-one would be able to locate the number so the complaint would go nowhere?"

Stupid Customer - "I am demanding that you give me a telephone extension number, I will be complaining about your poor customer service and your refusal to give me your number!"

Me - "Er...okay then ma'am. The telephone extension number that I am making up for you is 133497?"

Stupid Customer - "THERE! Was that so hard?!"

*CLICK*

Ooooo-kay then