Mtn
2GB data Promo cancelled with no warning

I subscribed to a 2GB data bolt on bundle in April 2012, and was paying 149 per month.
I recently called call centre in early January 2013 to reduce my bundle to 1GB as I hardly use 2GB. I was then informed that the 1 GB is more expensive than what I'm paying now. A minute later call centre agent Informs me that there is an error on the system and they have been undercharging me Since July 2012, and threatened to back charge me the balance. This is extremely unfair and I am sure that I needed to be informed that the promo was ending.