Telkom Account - Harrassment - NuDebt Management

I have a Telkom account that was handed over to NuDebt Management. I am under Debt Counselling at the moment. After being compliant and paying both in January and February 2016 installments they sent me a letter of demand and threat for not paying. Now they are harassing me daily and the amounts I supposedly owe change every time. Last week the amount was 320 then it was 520 and now they say 379. As you can imagine I no longer trust their admin and any amounts they claim I owe. I have sent them several requests to contact my Debt Counselors and they have ignored all of them. Even after my Debt Counselor contacted them I still receive threats of legal action, phone calls, and sms's on a daily basis. I am fed up now!