Impossible to cancel FNB SIM

I am trying to cancel my FNB SIM. 1. Contact premier suit...they not able to help (useless as usual). They did give me a number to call though. 2. Call FNB SIM number to cancel. They take all my details, say I will be phone in the next 48 hours to confirm I want to cancel my SIM. Sounds simple enough so I thought ok its done. 3. Receive phone call that is marked FNB SIM on TrueCaller. So answer the phone, only to not be able to hear anything from the other side. Waited on this call at leas t 30 seconds...nothing. Happened 2 more times then nothing.

Currently, my SIM is STILL NOT CANCELLED. Still getting BILLED. When a cancellation process is not working because they for some reason can not phone me, is really annoying.