Help with a small claims judgement.?

Earlier this year, I was summonsed to small claims court by a car dealership for $800. As the defendant, I showed up at the court on the date of the hearing, and the plaintiff did not, nor did they have any respresentation present. There were at least two others who were there for small court claims by the same dealership. The judge granted me the default judgement, with prejudice, based on the fact that the plaintiff did not show, nor had made any attempt to contact the court for a reason why. I just received another notice from the same dealership for the same matter in small claims court. Can they do this? What can I do about this?