I don't know if this counts as a help-desk story, but it happened the same time I was doing technical support. I used to work for a pretty large national ISP. Our policy at the time was you could only refund two months worth service fee.
One day this guy calls in complaining that he cancelled his account ten months ago but he just looked at his credit card statement and noticed he's still being billed. He wanted all ten months refunded and wouldn't take no for an answer. I tried to explain that two months was all he was going to get, no matter what, when he tells me, "Look, you stupid bitch. I want my money!"
I had to put him on hold for a minute and speak with my supervisor. My supervisor gave me full permission to deal with the call as I pleased short of swearing at the guy or threatening him. (Our call center was threatened constantly if that gives you any clue who the ISP was.)
When I picked him back up I asked if he had his credit card bill from the month before. He said yes, and yes, the service was listed there.
"Okay, do you have your credit card statement from ten, no, let's make this easy, six months ago?"
He put me on hold and dug up the bill and yes, yes our service was listed there as well.
"Okay, sir. I think from this line of questioning we have determined this in no longer a billing issue. This is an optomitrist issue. You'll need to speak with your local optomitrist--he may suggest glasses, contact, eye drops, what have you. Speak with him and have that taken care of, call us back, and we'll refund your two months."
"What?! What did you just say?! What did you say to me?!"
"Ah, sir, this has just been escallated to an ear, nose, and throat specialst issue. You'll need to speak with him--he may suggest ear-drops or a hearing aid, speak to the optomitrist, then call us back and we'll refund your two months."
He hung up.