Account cancelled but still getting measages from Debtors

I had an account with Telkom and cancelled it January 2017. I called the Call Centre and they confirmed it is cancelled. Before that I was handed over to the debtors because Telkom cleared my account but did not clear the billing, so now I am being bombarded with messages from debtor companies. If I call the company no answer, they emailed me and I responded and no other response from them. Telkom’s billing department is pathetic, I am frustrated with the way things are being done with there billing department. My account number is, ********** 41699.