This is called an option contract and it's not at all shady unless you do it they way they have done. Basically you can come in to a dealership and make a deal on a vehicle. If you don't have financing arranged you can give the dealer a down payment and sign a standard contract that says you have X number of days to arrange financing and bring them a check from the bank. Otherwise, if you can't arrange your own financing, the dealership will arrange your financing, generally at a horrendous interest rate.
Sounds like you signed the option contract, except you had your trade in as part of the deal. You came back and took the used car part out of the equation, which any normal dealership would just say ok and move on from there and get you financed at 12% or something. They're just being dicks because they must have been stealing your used car from you and knew they could recon and sell it for a nice profit. The were already going to make 3+ points on your financing, but they're being greedy assholes and wanted to hose you on your trade as well is my guess. You should have asked to speak with the general manager or at worst general sales manager and told him what was going on.
It was the general sales manager that kept telling me that I technically bought the car already. They gave me two options and about 10 minutes to decide. I either bought the car with the contract I was lied to about (wife and 13 year old were present in the finance office.) Or work another deal on the car.
There was no option NOT to buy the car. Had I chose option 1, they would have had to report my car as stolen because I never took their car off the lot because I was confused as to what just happened.
I was forced to take the 2nd option. Here is the deal. The 2nd option was the exact deal I came to the dealership to make, willingly. 2.99% interest through a Credit Union that they found.
What I dont like is they forced me to be a customer. But, now they are forced to have me as a customer.
I cant post the dealer, yet. Ive been hitting all the review sites and the general sales manager left me a message that said he remembers my actions from yesterday in a threatening manner. They might suit me if I tell my side of the story. And from what I have seen, they love suing people.