Exorbitant charges for data

I recently had the misfortune of having no ADSL service from Telkom and was forced to use data on my MTN service to access the internet. I was very careful to only use this option when absolutely necessary and then only for very short periods of time. I then received the shock of my life when I got my first bill from MTN for data usage. The first bill was just in excess of R1800 just for data usage. Worse news was to follow. The next bill was for over R3500 for data usage. when I questioned this with them I was told that this was out of bundle charges. I had used approximately 3.5 gigs of data and was charged R3500 which works out at roughly R1000 per gig! Is this even legal? How can MTN justify charging such an exorbitant amount for data usage. This is just unacceptable. Is there no regulatory body that sets the maximum charge for such things? We are the helpless cash *** for these greedy corporations. Shame on you MTN.