MTN disgusting service

I contacted MTN customer service on 23 December 2015 requested a consultant to load 1gig on my number, she loaded 20gig instead, I called them the nextday to notify them of this, the consultant said the 20 gig was not reflecting, she could only see the 1 gig that was loaded, 2 days later my number was suspended due to limit exceeded, I called them again only too find out that my running balance was R1500 (I have been billed for the 20gig), I called over 10 times to get them to reverse the error, finally the 20 gig was reversed on the 5th of Jan 2016, but the running balance remained the same, again I contacted the several time to get them to change the running bill before it was released and finally some consultant told me it would take about two weeks to change the contents of the bill and that was on the first week of January 2015, I was shocked to find out on the last week of January 2016 that my billed was not changed and I was charged for the 20 gig loaded in error on my number, I am up to this day I am waiting for them to refund me, the managers have been promising to call me back, I want my money back immediately, not next week not after a month within 24 hours.