Roped off by content charges

I have been a loyal client of MTN since its glory days when they opened with prepaid but now I feel I'm being given riped off by content service charges . And the consultant tells me they have no way of stopping it from happening. I have a modem line 4 the years and it's strange that in the last 2 months my bill jumps by R400.00 only after my own investigation find out its content charges .