Poor customers service on first time car buyer

I bought a Hyundai I10 in 2021 September it was brand new and as a first time buyer without any technical knowledge regarding service intervals. For the first service I receive phone call regarding 15 000 km service which was in 2022. And when I visited the dealership in 2024 as the car was on 30 000 km I was told that they cannot do a service on my car as I have skipped the service interval. Of 30 000 km. it was strange news from the dealership, how can they refuse to perform a service when the car is still under service warranty and I was told to pay R3000 so that they can perform a service I am very disappointed by the treatment received from Hyundai The Glen. I am very much disappointed as a first time buyer. Currently my car is on 35000km and they are still refusing to perform a service. Please assist so that I can get my car serviced. Kind regards Tshimangadzo