BILLED FOR SERVICES I DONT USE

I renewed my contract 1 year and months ago, I was paying R169 for the blackberry 8520, then I renewed it to blackberry z10 that I still had to pay R169. it was to my surprise when I opened 1 of my statement and it was billed R230, I then called the MTN customer service and they told me to visit the branch and that is far from were I stay I went to the branch when I got there the lady who helped me told me I was billed for BIS, it is surprising because z10 doe sent use BIS it uses data when I asked her the way forward she told me she can only deactivate the charge of BIS I then asked about the 1 I've been paying without usage she told me there is nothing she can do. R69 I've been paying for almost 2 years its a lot of money n the question is where is that BIS going. I need my money back