Precision Plumbing Tried to Rip us Off , tell us we need to do this / that to get our water heater working Properly etc. Las Vegas, Nevada

We were informed to have a tech come out in 2/09/15 inspect problem then informed It would be $385. We told Robert it was to be Free Estimate. Then he suggested us buy the protection Plan cheaper for the flush. We did  Had tankless water heater Flushed 02/23/15. The flush Did Not solve problem. In the inspection of our tank he Did Not! See any Reason that the Sensors would Need replacing. Then we called Ranni Co. Find out ALL warranties. 3/3/15 he came back to inspect more of problem. came up with $ 760.00. 1st then stated $720. For installing future parts from Ranni Corp. After conversing with Ranni techs. We do not believe he capable of Knowing what he is doing. He supposedly spoke to a Ranni tech. But there is no order in which Ranni has on file to send us parts that he is to install for us. No one at Precision had called back all day as ms Rhonda was to. She sent him back here today (3/3/15 at No charge. There is lot ?? To be answered