What options do we have if used car dealer refuses to do repair stated in "WE OWE" contract signed by both par?

My wife and I purchased a used 2003 Land Rover from a used car dealership about 2 months ago. We noticed during the test drive the A/C wasn't working. After negotiating we stressed that the air needed to be fixed to have a deal. We got that in writing signed by both my wife and finance manager in a "We Owe" contract form, clearly states fix air. Ok so we brought back week later, a salesman who doubles as mechanic because they don't have a shop on hand, tries recharging A/C doesn't work. Tells me to set up appt. for next week he was going to order parts. Brought the truck back, 30 miles away from house by the way, saleman/mechanic starts taking stuff apart and the guy tells me the parts place gave him the wrong. Getting very suspicious at this point start talking to the guy about taking somewhere that will actually fix it and he tells me big money and I tell him we have a written contract to have it fixed I don't care about the price and he tells me to talk to my salesman and finance manager. Weeks go by my wife and I call them and tell them we are not happy and want the car fixed or returned and they only tell us to bring in and trade for something else. We are not going to lose money on a trade when we have a written contract for work to be done. Just spoke to the finance manager the other day and he tells me they only agreed to recharge A/C, didn't want to argue with this guy, he abruptly tells me he has to go to a meeting he would call back. Three days later no phone calls. Playing nice doesn't work. I'm done at this point. I contacted States Attorney and some lawyers. Is this breech of contract? Can we sue to have the car returned and have the contract null and void?