Struggle to get an expired contract cancelled

On the 27 October 2017 I have cancelled a LTE contract with Telkom which has expired end of June 2017. We have decided to go the Fibre route - with Telkom. I have followed this cancellation telephonically up several times by dialing the 180 number, on several occations I was promised they are busy with cancellation and that they have fast track the proses. On 6/12 I spoke to a Mr Mabosha, which is a supervisor at the call centre, confirming that this is still not cancelled. I keep on receiving sms to upgrade my contract and I am still charge for this service which has been cancelled. Mr Mabosha promised me that this will be cancelled ASAP. Needles to say I am still getting billed.