Partial refund on ********** upgrade

I have written two reviews on the reimbur*****t of the unauthorised debits from my sister's bank account, to which Vodacom's immediate response was that they will appoint someone to investigate the matter..... However, for both the last two reviews, I never heard from Vodacom again. I don't understand what needs to be investigated. R11 242.96 was erroneously debited and to date R6 535.11 was credited back to her account. The balance, R 4 707.85 is still due. It's really not complicated, and yet in spite of the first review being submitted on the 2nd December and apart from their automated response to the review, I haven't heard anything whatsoever from Vodacom. Does ANYONE have any suggestions as to how I can escalate this? Please.