Gall Plumbing

We had a problem with our gas water heater shutting off on its own. Gall plumbing sent out a plumber who took apart the burner reassembled it aproblem never said any possible problems or causes. We received and paid the bill. A couple weeks later same problem I restarted the water heater. Went out for a third time so we called Gall plumbing again. They sent someone over to look at it. After stating thermocouples either work or they don't he installed a new thermocouple and stated we wouldn't be charged labor. A week later we get a bill for $70! Lowes sells thermocouples for less then $10. The first visit from them was pointless in solving our problem and the second visit we were just screwed by price gouging