Unauthorized deduction and unprofessional service

I am angry and disappointed in the way Telkom treated me, for some time I have been receiving treats from companies claim to be debt collector saying that I owe money which I don't know. The worst part is one of them has debited from my account which I manage to reverse. Now I have new one NDC also saying to avoid legal action I must pay R2 200,45 which I don't know. I tried to call their customer service they don't know that. This is unprofessional for such a big company like Telkom to send my banking detail to people without my concern. this is uncalled for Froud.