Begging Telkom to clear my name

My experience with Telkom has been horrible. In March 2018 i went to the shop to cancel the contract because it has ended. I was given the form to fill and send to cancelation department. They never acknowledged receiving the form, instead the amount kept increasing every month even when i had stopped using the contract. I kept calling, sending email, communicating via DMs on Twitter to tell them i canceled the contract, instead they listed me on credit bureau. I find out when i try to buy a house in 2020.Now i cannot buy anything on credit. I then decided to pay the money i don't owe so that my credit score can improve. I payed in 04 November 2020.was told i will get the cancelation letter after 15 working days. I never received a letter. I now follow up every week and im told the same story every week that they sent my query to cancelation.. When the contract was valid, i never missed any installment.