Faceless Vodacom with no ownership of issues

On 16 February I received a call from Vodacom to inform me that they investigated my out of bundle data usage and decided to credit my account with R920.39. The total charge for data was R1534.22 per their analysis. I have called Vodacom repeatedly to explain that I never went into out of bundle rates, and that I did not call them to investigate the usage and pass a credit. Several hours on calls with various departments have proven futile to get an explanation of who/what caused Vodacom to start investigating the data usage. Generally, the customer calls in to trigger such a request but they have no such record. I did not receive my February invoice as yet to review the charge and raise a query, so it is puzzling as to why Vodacom triggered this on their own. Which leads me to believe that they have been incorrectly charging me at out of bundle rates, because I disabled my data usage on my phone as soon as my in bundle quota was used, which is my standard practice that they can confirm on my billing history. Nobody is willing to get this resolved. On my last call yesterday (ref no ***) the supervisor was to call back, which never happened.