No outgoing or incoming calls

Changed from contract to prepaid on the 23/09/2020 and was no longer able to make or receive any calls. It's been 6 days now without being able to make or receive calls. I've called their customer service number to little or no assistance and at times being put on hold for more than an hour. I've also went to an mtn store for assistance only to be offered no help but told to call the customer service and when I do that I'm told the same thing that it is sorted and I just need to restart my phone however I'm still not able to make or receive any calls.

This is one of the worst experiences I've ever had and they have no regard as to how this affects one's life