Telkom's Useless Retention and Cancelation Department

Telkom retention and cancelation call centre not answering their phones, I have been trying to convert my cellphone contract back to prepaid as it ends today, for weeks on end I have been calling the number without any answer. This is frustrating as I have no time to go to service centres due to the nature of my work. I think this is the end of the road for me. I don't want to see and hear anything Telkom going forward.