Client: Hey, you're the IT guy right?
Me: Hey, how can I help?
Client: Yeah for some reason I've lost power to my computer
Me: *Checks power, all computers are down due to a power cut*
Me: You'll have to contact your power supplier as you've lost power to all computers and lights.
Client: What, but the computers are not working right? - that's you're job not mine
Me: That's not how it works.
Client: Fix this or I'll bill you for the loss of money we've encountered during this and report this to your boss.
Me: How about I bill you for my time and advice and inform by boss that you tried to blame me for a power cut.
Client: You can try.
Me: *walks off and puts time in the ticket, requests purchasing to send an invoice*

2 Days later:
The client does not pay the invoice.
Me: (phone call) Hi, an invoice has been sent to you and we haven't received payment yet.
Client: were not paying that, you broke our power and made our computers break
Me: null