Registration is usually linked to the VIN on the chassis. Either someone told you the wrong year of chassis, the registration is wrong or the VIN was read incorrectly. This list http://www.thesamba.com/vw/archives/info/bugchassisdating.php is pretty definitive for the chassis' years. Double check your VIN (stamped on the top of the tunnel behind the seats) with the numbers on there and see what you come up with.