RG2500 Warranty question

I purchased an rg2500 reg setup almost 2 years ago.
I purchased it at Ginnie Springs. The shop that I am
with back home is also a Dive Rite dealer. I had the
reg. serviced there 1 year after it was purchased.
When I paid for the servicing I also got charged for
the parts. I had the receipt where I had originally
bought the reg. and showed it to them. Is there
something that I need to do before the next servicing
or something that the shop needs to turn in to get
the parts for free? I thought that the warranty said free
parts when serviced. Please Let me know if I misread something.

Thanks,
Scott