Just bought this car and when it is cold it.

Just bought this car and when it is cold it would not change into 3rd gear.I took it back to them and they said I was driving it wrong and nothing was wrong with the transmission. I went and got a second opinion at a transmission shop. They tested it and the code popped up saying 1st and 2nd shift selenoid vavle. I took the car back where Im buying it from. Told them what I found. Asked them why they clear the codes out. So now theyve had my car a week today. Gave me a loaner car.2013 Buick Verano. Punks. Anyway, I called this morning. They said it is my torque convertor and have to see if insurance will pay for it. Remember I found this problem with my car 6 days before my 30 day warranty was up. Help me.I am a 33 year old woman who knows nothing about cars and car lot laws.I got the car from Sunrise in memphis tn.