You must have negotiated free warranty service when you bought then. I had to pay for everything with mine. The only things that were free was if anything broke when it shouldn't have.
Some vehicles come with free service for the first 3-5 years. Usually higher end type cars. The BMW I used to have had a little screen come up telling you when your next service was required and this changed based on vehicle use. The dealership couldn't do any maintenance until the time was up. I got a let a couple of times because I brought the car in so infrequently I just got service once a year. The car I have now gets free service but it is just based on time or miles, so I take it in every 6 months.