Impossible to cancel services

In November 2017 I assisted a friend of my father with an issue he was experiencing with his email. It turned out that the issue was caused by a very slow and unstable internet connection. At that stage he was using a Telkom ADSL connection. We logged numerous faults with Telkom to resolve the issue, but all of this was fruitless. Eventually he decided to move to a 4G wireless connection which resolved his email issue. Since then we have been trying to cancel his ADSL line and Telkom ISP service without any success and Telkom keeps calling him and threatening to cut his telephone service which he still wants to keep. We have sent them an email detailing all his services and specified which ones he wants canceled and which he wants to keep. He has been to a Telkom office in Centurion mall to try to sort out the problem, but apparently it is impossible to speak to someone in person as they only phoned someone from the store and had to once again try to resolve the issue over the phone. He has now once again reveived a call from Telkom demanding payment to prevent the suspension of his service.

At some point I had hope for Telkom thinking that they might have sorted out their bad service, but they are obviously just as useless as ever.