Charged +- R300for internet usage unknowingly

Good Day<br> <br> I upgraded to a samsung last year November and this meant that I no longer got BIS. The deal was that I would get 500MB of data and my call line woiuld be opened. Every month since then when my data was depleted I would get a pop-up message telling me and I would be unable to use the internet nor log on to social networks. This month I did not receive this pop up and I checked my data balance and I still had data. I got suspicious when I noticed that within a week there was minimal movement in my data balance, so I checked my unbilled balance and noticed that my call charges were +- R300. Now I know my usage and this was ridiculous so I called 808 and I was told that I had an open line, now firstly since when does this open line apply to data because this wasnt the case for the past 4 months, secondly when did I agree or sign a contract stating that I want an open data line because my calls were opened since 2010. I would expect call and data charges to change and/or fluctuate but I would not expect the conditions of my contract to change without my knowledge. Its unprofessioonal to start charging people without their knowledge. I feel disappointed with this shadiness.