If I did not know I signed a contract is that contract void?

I went to a car dealership and I thought I was signing that I acknowledged that I got approved for the loan. He has incorrect information on the "contract" and I don't even have insurance. He never took any proof of residency, he knows that I don't have insurance, I told him afterwards that I didn't want the car and that's when he told me that I signed a contract. I told him before that I was just wanting to see what everything would look like if I trade my truck in but that I wasn't sure that I would trade it in. He says that it would not be a problem. After I told him that I didn't want to trade my truck in he said that I already signed the contract. I never left with the vehicle and there was never a bill of sale on either part.