Transmission Slip Out Of Gear problems of the 2004 Lincoln Aviator

My main problem is that the car has an intermittent transmission problem. The car slips out of gear and the engine races. I have mentioned the problem to the service department on several occasions and they tell me it?s my problem till it does it for them. The other day I got a letter from Lincoln saying that the factory had put the wrong transmission fluid in the car. The service department still does not think this is my problem. The car has been in for the ac being broken; the brake rotors have been replaced. The car makes a loud noise on start up and they told me it was normal, however I have asked other people with my molded car and the said that there car makes no abnormal noise on start up. There is a problem with my steering when the car is not in motion. Other problems are minor including some small electrical problems. My main concern is that the car is dangerous to drive and they just do not care. In the mean time when I brought the car in the last time for the transmission the service department said they would keep an open order on the car. The big surprise is that they lost the order as I have requested a copy of it. Please help harold bennett.