Contract in bad faith

I got into a contract with MTN in March for an amount of R354.78 and I was advised of prorata charges for the first debit , in April and in May my instalments hiked up unbelievably to R2046.02, I then went to the branch where I concluded the contract to ask where this high billing comes from, I am told the usage was never capped , and they DO NOT KNOW WHY, I never asked for this in the 1st place I specifically told the consultant who helped me to CAP IT, there is nowhere on their contract where it says I signed for an option to have an uncapped usage.

I went on to ask the consultant if this can be capped while I go on with my complaint and she says they cannot cap the usage because they need to do another billing( meaning they need to bill me some more), I have been treated unfairly , things that concern my hard earned money where done behind my back for MTN`s own benefit, I intend on escalating this to CPA , I am not resting I want my money.

I do not even want to imagine how many people who aren`t litrate and know their consumer rights they do this to, PURE DISGUST.