Vodacom Indulges in my bank account

I had a contract with Vodacom - for R149 per month I would receive 2G during the day & 2G after midnight. It was a 12 month contract but I was happy with it and continued with it for years, even when better deals came on the market. For a short while the amount debited from my acc dropped, and I thought an adjustment had been made due to the fact that I was an old customer and there were generally better deals to be had by then. Then, the amounts debited began increasing until Vodacom was taking up to R2000 from my account causing my bank account to bounce at times. When I enquired I was told I had used the data. I explained that I had a capped bundle and should not have been able to use any more than my agreed 2G per month. I was told I did not have this bundle. I had never changed my bundle that had been adequate for years. Vodacom just insisted that I did not have that bundle. I asked that my account be frozen until this problem was resolved. I was told I could not do this until I paid the latest bill of R2000. The agreement I had with Vodacom was 2G for R149 per month. This is what I gave them permission to take from my account for a capped amount of 2G.