Vodacom is billing me for data I'm NOT using

On 28/09/17 (Thursday) I checked my Vodacom account and I had been charged for R800 of data usage, Vodacom claim they sent me an SMS on tuesday 26/09/17 which I DID NOT RECEIVE, meaning that in 2 days I spent over R800 in data when I have wifi at home AND work. I then purchased a data bundle AND TURNED MY CELLULAR DATA OFF! Only to find the following day Friday morning 29/09/17 my bill increased by another R400?? My cellular data remains OFF and when checking again Friday evening the bill has increased by a further R100. Please explain how a total of R1300 data can be billed in a space of 4 days with NO SMS notification sent out to inform me that data is complete AND with a data bundle in place AND my cellular data and wifi assist all turned OFF?? Vodacom need to take responsibility here and reverse ALL these charges.. I have called and complained and they argue with me saying it is my usage.. I was also informed that I would receive an SMS with a reference number for a dispute logged which to date I have not received. Vodacom, jack up yourself and sort this problem out FAST..