I showed up for an internet down call at a restaurant we supported (ISP already confirmed it was an active and working connection). The owner was flipping out yelling at us for breaking the internet, blah blah blah. We told him flat out ahead of time that if it was something he did, he was being billed double time based on the time I left my house, till the time I got home. He agreed right away because of course it was our fault.

I tested the whole network, confirmed that all the cabling was good (he always had issues with rats eating his cables) and was at somewhat of an impasse. After another half hour or so, I figured his router was probably bad. I climbed up into the ceiling to take it down, and low and behold, I found a cable looped onto the router. Unplug it and boom! internet.

This of course leads to a long 'discussion' about how that cable was installed like that when the system was put in about 5 years ago, and how he was never going to pay for this call. I demonstrated by plugging in and unplugging it, like "see? internet works, internet don't work. It isn't possible to have worked like that, someone clearly hooked this up."

I didn't find out what happened with the billing for that, because I said fuck it and left it up to the other department.