Billed for cancelled service

We are STILL being billed for a service which we cancelled on 6 October 2017. I sent through an email on the aforementioned date, with the completed form that we were told to fill out in order to cancel our service. We are still receiving accounts for this service. I went onto the Telkom site and low and behold, someone has once again not been doing their job!! Our landline has not been cancelled and we are still being billed for ****! I REFUSE to pay the amounts that are on there. Get your act together Telkom! Sort YOUR mess out.