Being overcharged

I upgraded my phone in July. I saw a special for the Huawei for R299 a month which included 100 min, 100 sms and 2Gig. When I phoned, I specifically told the agent I want the deal with the 2 Gig data. Two months later, I checked my bank statement and to my shock and horror saw that I was paying nearly a R1000. Checked my mtn statement and saw I was being charged R459 per phone WHICH IS NOT WHAT I AGREED TO. Went to the walk in centre and was told about some 1 Gig data **** that wasn't cancelled. Which I still don't get because I never asked for and extra 1 Gig data and I never had such a deal ever. I was also told that there was a 2 Gig data special for July but it was R329, not R299. I said that's fine, I will still pay that, but not R459 per phone. A query was lodged to get the call, but it has been a week and I haven't received one email, sms or phone call to see how far this problem is. The next deduction date is almost here and if another R1000 gets deducted, I am taking further steps