Data bundles not activated

I buy a top-up data bundle every month when my standard data bundle is about to run out. Since November however the bundle does not activate even though the transaction is created and visible on the website. I logged a call with Vodacom on 21 November, and have since spoken to 3 agents. Apparently my call was forwarded to the accounts department, and for 2 weeks I have heard nothing. Now I am about to be billed at out of bundle rates for November, and the cycle is about to repeat itself for December.
Any advice on how to get action on the call? Continuing to call 111 appears to be an exercise in futility