Service to automobile

My vehicle was mis-diagnosed for having a bad solenoid. I was charged $409 to replace a part that was not bad. I had the part tested at Arnott Ind and I even talk to the machanic at Palm Bay Ford that stated that there was a leak around the part, but he did not know if it was bad. He was advised to change the part out by John Davis. I had the same problem with my vehicle after it was serviced. It was initially diagnosed needing a valve, strut and compressor at over $1,400. The valve and struts are lees than nine months old. After I told them that I wanted the old parts, it became that I only needed the valve. I took my vehicle to Blvd Tire in Orlando and they found out all I needed was an upper mount (sets on top of strut) and to replace the ORINGS. The dealership refuses to reimburse me for doing work that was not necessary.