Telkom useless in cancelling contract

We've cancelled Telkom 7 months ago. No refund on the deposit and the line has not been cancelled yet. Now all of a sudden they are threatening with ITC. We have been to a Telkom shop, but even the employees need to phone the call centre, ending up with a call, full of promises and a reference number, only to receive an invoice again where the monthly instalments keep on accumulating. No help from TELKOM!