Overcharged

I have been charged unnecessarily , around R800/R900 extra. I was told that I changed the settings to be able to use out of bundle , I am not sure how or why I would change it for me to then complain about it later? I know for a fact my first 2/3 months I used to get a notification saying that I had run out of bundle and I needed to load more data, from one month to the next it changed and I longer received that notification and I was automatically charged out of bundle rates. I will not stand for this and I will keep making a noise about this until I have an answer!