Refusing to cancel my contract and extended it with another 2 years

I took out a contract with vodacom July 2017 in August 2019 I contact vodacom to cancel my contract. The advisor who assisted me refused to cancel and advise me they can still give me 10GB of data once off, I asked advisor can I still phone in and cancel anytime which he said yes.. December 2019 I contact vodacom to cancel they advise me they can't cancel the contract has been extended till 2021 and there is a settlement amount of R5000 if I want to cancel... So why should I pay again for the same phone for another 2 years and on top of everything the advisor was so rude. She had a attitude and said mam I will not cancel you agreed to till 2021. Vodacom please fix this