Vodacom - my contact is complete - stop billing me!

I have been waiting to have my cellphone contract end. October 2020. It ended and I immediately canceled. I had my number changed to prepaid. I paid my contract in full, then in November, I got a message saying that I owe R600+- which I paid the moment I got the notification (in November 2020). My confirmation, for changing to prepaid came in around the 4th of November 2020. Vodacom is now billing me for 3 months. Saying that I owe money because my contract was not SUCCESSFULLY canceled due to account in arrears. My account was paid in full and when each time I got a notification (which I did not even see as reasonable because I was NOT in areas but thought this was for October 2020) so paid anyway... Point 1. Canceling the account even after the account was coming to fulfillment was a nightmare. It took many many phone calls and going to the Vodacom shops over 5 times. 2. Once I canceled it, it and moved my number to prepaid, which means, no contract, how can I be billed for November, December 2020, and then January 2021? Balance brought forward? When I have canceled my contact ages ago. Contact me, please. I won't be paying for this. It is not fair and no one let me know that my contract was not successfully canceled. The lady handling my account said it was canceled.