I worked as a car salesman for a few months when I was younger and didn't yet know what I was going to do career-wise. Although I did not see what you signed, it seems as if you only signed the "sales order." When I was with a customer, the question always was "what would it take for you to buy today?" "OK, then sign here and I'll take it to my manager." Sound familiar? All this is to make you "feel" as though you've committed to the deal. They will have you sign for a purchase price, a monthly payment, anything to make you feel like you bought the vehicle. Unless you went into the business office and signed paperwork, you didn't buy anything.
Again, let me state that I did not see what you signed, nor am I a legal expert. This is my opinion based on my working as a salesman and also from my experiences purchasing numerous vehicles.
Edit, I just thought of something else. You can sign the paperwork agreeing to the price with the salesman. Then you go into the business office. In there, he presents all the options of warranties, clearcoat protectant, length of contract, and interest rate, etc. If you can't reach an agreement in the business office, you don't have a deal. Plenty of times I was trying to purchase a vehicle at a certain payment. (no lectures please). Plenty of times the salesman said, sign the quote and lets see if he can work it out in financing (business office). If they couldn't get to where I needed, I was done and thanked the salesman on the way out.
