Bad service

I had a contract with Telkom, after failing to pay a couple of months, my account was handed over to a collection company and I paid up what was owed and got a paid up letter from the company Debt In. Now I received another collection request from a different company on behalf of telkom for the same account. I called telkom and they told me that the account still accumulated more fees after it was handed over for collections to debt In. How does it happen that an account still accumulates fees after being handed over for collection to a debt collector? Telkom can't even give me anything in written that explains this terms or conditions. I've received the worst experience with Telkom, even the consultant couldn't even assist