Vodacom refusing to cancel contract because I don't want to get another contract

Last month I sent a notice of cancellation on the 28th of September for my data contract. I didn't receive any confirmation or feedback that my email was received and being processed. On the 7th of October I called the cancellation department to check if my email was received and the person I was talking to instead of confirming it the email was received he was busy trying to convince me to get another contract. When I refused to get another contract he said he can't give me confirmation about the email cause I didn't ask for confirmation when I sent the email so I should send another notice of cancellation and this time I must ask for feedback.