Time to invoice again ---

You get a call to quote for a job ... things are a bit tight ... you are between projects and need something to fill the gap ... you arrive on site and walk through the site with the customer ... offering advise were you can (thanks to your years of experience) ... he asks if you know anything about geysers ... you on site you ... you climb in the roof and repair the geyser ... finish up with the customer 1.5 hours later and head back to the office ... complete the quote and send it ... a week later no response ... you call ... the customer got a cheaper quote.

So you send him and invoice for the time to repair the geyser ... that were the fight started.