Bubba's Spray Equipment

been taking our machines to "Bubba" for almost 4 years, always priced high but kinda understood because what he does is a very specialized service, BUT last time we took our rig into him was a bad situation to say the least, I told him the rig was not pumping and they said they would get it on the table and check it out and call me with the diagnosis. His assistant who actually was a decent guy called me one hour later and said the rig was ready and the problem was that a seal had been installed backwards the last time it was serviced and thats was the reason it not working anymore, so when i go to pick it up he hands me a bill for $180 2 hours of labor and one $7 seal.. i told bubba what his assistant had told me about the backward seal and that he is the only person that has ever serviced it. At this point Bubba became very angry and started shouting and threatening to keep my 3,000 dollar machine if i didn't pay up, he denies putting the seal in wrong although i have records of him servicing it and no one else has ever touched it.. i payed him but i will never take my equipment there ever again and i warn any who considers.