Vodacom accounting

I have a data contract with Vodacom which expires on July 9 2018. The price paid monthly is R437.72 less a CIB discount of R175.44, amounting to about R300 per month. I decided not to extend this contract when it expires and the consultant I spoke with persuaded me to extend this contract at a special price of HALF of my current subscription, ie R150 per month. I agreed to accept this offer. I an debited on the 1st of the month and this month Vodacom have debited me R500 for my current contract without allowing the discount. After spending at least 3 phone calls lasting over 3/4 of an hour, being transferred from cancellations to accounts innumerable times I was informed that as my contract was cancelled (Expiry 9/7/18) the discount no longer applies. In spite of trying to explain that this contract still has a month to go I am unable to get any satisfaction.