Cancellation of service

I logged a call for my faulty Telkom landline, after a week of no response I called customer service whereby I was informed that the technicians no longer attend to prepaid landlines. She suggested I call direct sales to arrange for the new prepaid landline with a sim card, which I did the same day. I have received no further correspondence and my bank account was debited with the monthly payment even though I had no service since the 8 March. I so irrate and now wish to CANCEL/TERMINATE my landline service from future debits off my bank account.