This one is a little dated (days of dial-up) but I'm sure you can relate...
CUSTOMER: My website is down!!!! I WANT IT FIXED IMMEDIATELY! I PAID GOOD MONEY FOR THIS AND I THOUGHT YOU SAID IT WORKED!! I TOLD EVERYONE IT WAS UP!!!
ME: I am on the website now. I checked the server and everything is fine.
CUSTOMER: Don't tell me it's fine. I am going there now and the site isn't there.
ME: Do you use a dial-up connection?
ME: Do you have a more than one phone line?
ME: You will have to hang up the phone and get on the internet to see the website.
CUSTOMER: (CALLS BACK) I went to the website.
ME: Good...no problems?
CUSTOMER: No...but I think I should get a discount on your invoice for the website.
ME: Why? Is there something else wrong?
CUSTOMER: You didn't tell me when you quoted the website that I would have to add another phone line to talk to a customer and be on the internet at the same time. I don't think that is something that I should have to pay for when you didn't even tell me.