On the face of it, it seems as though the dealership tried to recoup the other 50% that MB agreed to pick-up.

can you describe the parts that were replaced under the campaign?

it seems that when you take a car in for service you sign a repair order or write-up that connects you to the service printed on the write-up , usually the dealership will contact you, and get an O.K. if different work is needed beyond what is described on the original write-up.