Cannot cancel Telkom ADSL

I've been trying to cancel my ADSL since February. I keep on getting invoiced and have now been told that my account was handed over to an attorney yet it is impossible to cancel online. Even their escalations process does not work. I refuse to pay more monthly installments or the arrears amount as I have not used the service since Feb and I exhausted all avenues to try and cancel this stupid account. What must I do?