Product: Vehicle loan or lease

Met and online car dealer who appears to be selling a XXXX XXXX XXXX for the amount of {$12000.00} in New York. Decided to flight from Texas to New York to see the car. Met with the dealer and at the time the dealer never had the car in NY but mention he is just a dealer and if everything goes through, i will have to fly to California and pick up the car. The dealer showed me pictures of the vehicle and everything, along with the VIN number of the car. I told the dealer i have {$4500.00} to put down on the vehicle and finance the balance which the dealer accepted and mention he will will go ahead and do everything and the bank will reach out to me to set up a payment option on the balance which should be {$8000.00}. 
After making the down payment of {$4500.00} to the dealer, the dealer provide with information to go pick up the car in CA. Went to CA to pick up the car and to my surprise the car do not match description on the ad on XXXX where i saw the car and don't match description showed on pictures by the dealer. Even VIN didn't match and had high miles compare to the one he showed me but the time it was still a good deal to me so i left with the car. 
2 months passed and couldn't get registration or tag of the vehicle from the dealer which at the time the loan company " United Auto Credit '' had called me and set up a payment arrangement and the amount which to my knowledge and like the dealer told me car sale price is {$8000.00} but there will be tax and other fees excluded so the final price of the loan will be more than {$8000.00} after everything is included which i did agree to it. 
Made my first payment to the loan company " United Auto Credit '' and let them know i am unable to get registration of the vehicle or tag from the dealer and unable to even reach to dealer and seems to me the dealer blocked me or something because i will call and no answer. Unfortunately " United Auto Credit '' could not do anything either until 5 months later that i told i won't be making anymore until the car is registered because it is illegal to drive an unlicensed vehicle just for them to get back to me another 1 month later making it 8 months in total no registration and mention they have gotten the title of the vehicle from the dealer and i have to go registered the vehicle myself and i wasn't okay in doing that but i had to. 
I asked for documents to go registered the vehicle which they provided and the whole documents did make sense and even them " United Auto Credit '' can't explain it to me. 
- Documents and receipt from DMV shows the vehicle sold for {$8500.00} - Documents from " United Auto Credit '' shows a contract which i did not sign or had any knowledge at the time for {$21000.00}. 
I told them of the loan contract being inaccurate i will stop making payment until they investigate and revisit the loan. 
A month later they called me say they can do a loan modification to reflect the correct amount and even reduce whatever interest they have to 4 % but i have to make a payment and a sign a loan reinstatement which i did and after making the payment they never got back to me with any arrangement on the loan investigate the contract i did not signed. I called the company for update instead they are threatening to repo the vehicle because i told them i am not making any further payment until the complete the investigation and work on the amount that reflect what DMV knows of since it is reported to the DMV vehicle is sold for {$8500.00}.