S550 2009MY Service Maintenance Message

I picked up my 2009MY S550 in mid-August 2008. I noticed that the next scheduled Service A Message indicator was based on the number of days since
the manufacture date of June 2008 instead of the delivery date. I had the service department (Rusnak MB, Pasadena, CA, USA) reset the Service A message to recognize the delivery date rather than the manufacture date. They reset it to Service B. When I asked them to reset it back to A, they informed me that the 2009MY Service Message assigns random letters and they can't reset it back to A. They next letter may be L or Q or Z or whatever! They also said that the new 2009MY service schedule is no longer based on A or B schedule but on an annual schedule so the letters don't mean a thing. Is this correct? Is there really no way to reset it back to A?
Thanks in advance, Ricky
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