Hyundai car service

I'm disappointed with Hyundai I bought a car with Hyundai Ladysmith in 2021 December, the salesman said I need to take my car for service when it reach 15000km I took my car to Hyundai Richard'sbay today and to my surprise they say the service plan has expired I was supposed to bring it when my car reached a year apparently it was supposed to be brought in for service when it's reach a year or 15000km which ever comes first and it's my first time hearing such as a first time car buyer they were supposed to explain this as well.