(A lady came in to buy an iMac computer. After leaving, she called me 30 minutes later.)

Me: “Yes ma’am, how may I help you?”

Customer: “I thought these things came with a monitor? You told me it had a monitor.”

Me: “Yes ma’am, it’s one big monitor with a keyboard and mouse.”

Customer: “Well this one doesn’t have one.”

Me: Um…it’s the big black square on the front.”

Customer: “There is NO big black square on here.”

Me: “What do you mean? The whole machine is just a monitor; it’s the big black square above the CD Slot and speakers.”

Customer: “There is NO big black square. There are no speakers. You told me it came with a monitor.”

Me: “Ma’am…the whole computer is just a monitor with speakers and a CD Drive built in. Spin it around; it’s the big black square on the front.”

(I can hear her turning the machine around and around, and she starts getting angry with me.)

Customer: “Listen, there is no big black square, there are no speakers, and there is no slot for a CD.”

Me: “Ma’am…do you have the computer face down on your desk?”

(I can hear a big clunk as the flips the computer upright on the desk.)

Customer: “Um…I have to go now.” *click*

Related: PEBKAC (Wikipedia definition)