Purchasing excursions

[Virginia]

I need help....we just booked our first cruise on the Summit - May 20...looking at the excursions we saw we could take the train from Seward (when we got off the boat) to catch our flight in Anckorage...we booked our cruise/air package through AAA...now Celebrity is telling me that I can't buy tickets for the train because I have a cruise/air package...that you can only purchase the train tickets if you book your own air....does anyone know anything about this? Thanks..