Telkom inability to correct invoicing

I switched to Fibre from ADSL in August 2019. This also meant I canceled my landline/ADSL with effect from 12 August 2019. The August invoice was incorrect - I was charged for the landline/ADSL despite this being cancelled. I queried this and an attempt was made to correct it. The September bill still charged me for the landline/ADSL which I no longer had. The October bill has attempted to correct this again but it is still incorrect. And I am being charged for late payment interest despite the fact that the underpayment from my side is due to being overcharged.