Contract cancellation

I would never recommend Vodacom as a service provider to anybody. I purchased 2 cell phones on contract from Vodacom in February 2017. I knew that it is a 24 month contract so in February 2019 I called them to confirm when the last debit order would be and they confirmed that it would be at the end of March. I decided to call this morning as I saw that I had received airtime again. I was then told that I should have told the consultant that I wanted the contract cancelled. My question to them was why did the consultant not tell me that when I asked about my last debit order. Further to that, I was told that I need to call some department for them to listen to the call recording. How is it my responsibility if the consultant didn't do as she was supposed to.