Regional Hyundai

I recently purchased a car through Regional Hyundai about 3 weeks ago. They called me today and demanded the car back even after I got approved for no money down. They told me they changed their minds and now they want $2000-3000 down to stay and my vehicle and if I didn’t bring it back today, They were going to call the cops on me. I don’t see how they could even do such a thing of that nature to a customer. I thought once you signed all the paperwork that was it done, over with. This should be illegal, and I wouldn’t ever recommend you guys to anyone. This is so embrassing to me & my family!