Wrong billing not addressed

I called the call center early Jan 2015 concerning my Data account which I requested them to put a cut-off limit on, as well as to set my data notifications to be sent to my cell-phone, as the data device cannot receive notifications. The consultant agreed to do as requested. A while after that I went online to check my data, and saw that my account, which is a R 259/pm 5GIG data account, has accumulated to over R 600! I immediately phoned the call center again explaining the situation. She informed me that the previous consultant did make a note of my request, but never activated it. She then proceeded to activate the functions I requested. I told here that I will not be held liable for this mistake, and that they must clear the bill that was a result of their mistake. She agreed to escalate the problem to their management to resolve and said I would receive a phone call concerning this within 48 hrs. A week later I still had no response.To this date I have contacted them 3 times already. Every time I relate the same story, and get the same promise, but nothing happens. I do not know who to contact to resolve this problem. I hope someone at Vodacom can reply to this complaint.