Vodacom failing action my request for contract cancellation to become prepaid

My contract was paid up in July 2020. I contacted Vodacom and asked them to convert my line to prepaid. I was told about billing cycles but anyway, expected my last payment to be on end of September. I would then be fully converted to pre-paid by 18th October. I even called cancellations and they confirmed that nothing would go off my account as I was not subscribed anymore. (Meanwhile, I continued to receive calls from ladies offering specials on my 'existing contract,' and all the time I would tell them I am not interested and I have cancelled all contracts). Surprisingly, I have been ducked R154 today (3rd November 2020). I am trying to reach Vodacom - on contract platform they cant entertain me as I am now prepaid; on prepaid I land with a bot who effectively cannot help me. I do not want any more money coming off my account and need Vodacom to action this.