Paying for cancelled vodacom contract

I have a data contract with vodacom which came to an end in December 2020. I informed vodacom that I wish to cancel said contract as I have fiber installed and no longer use the data contract. I contacted vodacom in December 2020 to confirm the cancellation and I was told it was all sorted out and had been cancelled. January I was not only billed for this contract, but I was charged R345 for it, when my contract was only R150. I have since contacted vodacom regarding this matter three times and I am told my issue has been escalated and sent to higher management and someone will contact me. But three months later and no one has contacted me and I am still paying double for a contract I have cancelled. I will not open any contract with vodacom ever again.