Mitsubishi service rip-off

In September 2008 I bought a new Mitsubishi Lancer from a dealer in the western suburbs of Melbourne. In June last year I received a letter from the dealer clearly stating that if my car is less than three years old, or has done less than 60,000 km that the maximum I would pay for each of my scheduled services is $195 compared to the normal cost of $480, for example, of the 45,000 km service. My car complies with the requirements in the letter, being under three years old and having done 34,000 km, but when I booked my car in for its service I was told that the information in the letter was incorrect and that it would not be honoured. What can I do about it?