Yes, the best action is to report the matter to consumer protection department in the Ministry of Economy and Trade, who would take action against them.

German Center is old and surrounded by hundreds of car showrooms, who tends to create such deals by way of their old contacts with the staff of German Center. Any buyer or seller, should be avoided if he continues to insist on going to German Car Checking Center. But remember, there are others too, though on lesser scale, who are into this activity, because there is no control from any regulatory authority on them.