The car was purchased in California but repoed in Virginia where I had moved to a few months earlier. It was charged off before being repoed
Most likely they will have evidence they sent you the notice, even if you say you didn't get it. There's no guarantee a judge will believe you. If this is your most serious debt problem fighting may help you. If you have lots of other debts, too, maybe it's time to repair your credit by filing bankruptcy.
Before you spend any more money hire a lawyer and go to war, you might want to re-read the letter you said you did receive--the one containing the loan deficiency balance. Unless I miss my guess, that letter refers back to the notice you were sent right before they repossessed your car. If you do sue, you should also be prepared to tell the lawyer representing the car dealer how you found out that the loan had been "charged off" before they repossessed the car.
If you didn’t receive notice, you may have recourse again the lender.