This will still tank your credit score. The dealer will sell the car at auction, and if it sells for less than what you owe (which it will), they can still sue you for the "deficiency balance." What to Do Right Now
Navigating the "Rollback": Can You Return a Buy Here Pay Here Car? rollback buy here pay here
If the dealer let you take the car before your financing was 100% finalized (yo-yo financing) and they later tell you the terms changed, you can often refuse the new terms and demand a rollback. This will still tank your credit score
