Cancelled Telkom contract still being debited SIX months later

I cancelled my mobile contract with Telkom and am still being debited it for it 6 months later. Telkom acknowledged that the mistake was theirs initially but have done nothing to rectify it. I have spoken to them countless times, incl on social media. I am at my wit's end. I am being debited for dubious amounts every single month even though I am now prepaid