Telkom pathetic service

I have ended my subscription on 1 November 2017 with Telkom. After a whole year of figths with Telkom they admitted to deducting ********ly from me. The charges was finally written back to me exactly to the date one year later on 1 November 2018. Telkom still went and gave me over to ITC even if it was their mistake. I have now phoned twice (holding on the line for more than half an hour each time, 12.06.2020 and again on 18.06.2020) to sort it out. I was promissed that it will be corrected and I will receive a paid up letter as confirmation. Up till now 15 July 2020 I am still waiting. What must I do to just get the letter from them. It is pathetic to say the least. I am in the process of buying a house and it counts against me!!!! Telkom is the most pathetic service I have ever received.