Bad service and *****

I app**** for a car online in their website when i got there the car that i app**** for its not the same car as the car that was there, now the car its not even 3 months but its already giving problems. Took the car back to their dealership so that they can repair it since they said it has a one year warranty. It took them 3 weeks to fix the car after that they want me to pay a lot of money so that i can get the car back, of which we didn't agree on. if i wont pay that amount i wont get my car so they saying.