In your case if the financer have re-posseed the vehicle then he can claim the differential amount i.e. amount due - current value of the vehicle.
If the claim is exhorbitant, then you have all the right to defend yourself in the Court of Law. Further, if the statutory legal notice was not received you, then the same could be argued before the trial court. But the Court might ask you to give your say whether you admit/deny the claim, if you attend the hearing any as you have received the summons from the court and have attended the proceeding,
Adv. Rohit M. Dalmia