Nu Debt and Telkom Harassment

I cancelled a business ADSL and Data line with Telkom on 31st July 2019. I have provided copies of cancelled contract form handed in at Fourways Crossing branch, copies of proof of payments made on 30 August and 30 September 2019 as well as receiving an sms from a few months later stating that the account cancellation was no resolved. I have had in 3 years three different law or debt collectors harassing me despite me providing all the necessary proof. My next step is going to sue Telkom for threats and harassment. I will sue for a much greater amount just out of principal. *********** Muppets.