The most hilarious is when they come to work on my phone lines and the techs are asking me, "Well did you check to make sure the cord is in the wall?"
And I'm thinking, "You've got to be kidding! I designed and implemented telecom networks -- you think I wouldn't have checked the damn cord before calling?!"
It can be so infuriating. Every now and then, if someone is particularly difficult, I get quite snippy and start explaining how things work and what I think is wrong. My husband cracks up, but most of the time, my guess is right.
(If they'd listened to me the first time, they wouldn't have sent a tech out 3 times before finding & fixing their problem.)