Refund on telkom line cancelled

I have cancelled my telkom account on 18 Dec 2017 and still got billed til May 2018. No refund been done. My records reflect multiple phone calls to no avail. The constant message I get is that they will escalate it to the superior. Well they continuously say it every single time I phone. There is a disconnect between those poor telesales staff that probably get abused non stop but this clearly is a systems related issue that telkom need to address. I have paid up the account as I did t want to get blacklisted. No-one ever calls you back and responds to you.