"Error" during Vodacom service (non) delivery

For weeks now I have been unable to buy prepaid data or airtime via the Vodacom mobile app or the Vodacom website for my phone. When trying to pay I get a cryptic error saying: "There was an unexpected error during provisioning"...

Weeks ago I called the Vodacom 082111 call centre to try get an explanation for this and resolve the error, but all they could do was take down my details and send the issue "for investigation". They are unable to tell me what the problem is or what I can do to fix it...

Weeks later I'm still waiting for a solution. I called the call centre again and they could see the unresolved case on their tracking system, so they "escalated it" further (call centre speak for "passing the buck").

Again, after a third call to the call centre, I still can't get this resolved!

What must I do to fix this Vodacom?