Canselation of contract

I am very upset with vodacom. My contract expires on the 7th of november 2019, try to give notice to them to cancel my contract and not to upgrade again. Every time i phone vodacom the presenters tell me a different story. Fisrt you can not email them, then when you phone the cancellation department they say you van only give notice on the exact date prior to the ending of the contract which is 7th of october, i try but now it is not the right date i must phone on the 1st of the month on that month that the contract end which is 7th november. What is the right prosedure. Why is it so difficult to cancel a contract when it expire.