MTN over charging again, this after upgrading!

I did an upgrade in April 2015 on cell number and the April 2015 bill was fine. Then come May 2015 and I have been billed for Wholesale bundle charges for over R300!!<br> <br> What I do is I buy airtime and load this on my cell, thereafter I dial *141*2# and buy a data bundle with the airtime I loaded and I use my data as such, now a call centre lady that is very rude to start off with, tells me that it is correct?? I say that is bull! How can I be charged for data calls again when I bought a data bundle, this is double charging me for the same thing!!<br> <br> Everywhere I turn people are rude and do not want to listen nor use common sense? It is double charging!! I paid for the data up front and should not be billed for it again!<br> <br> I need this investigated, fixed and credited MTN!! May 2015 bill and June 2015 bill and every bill thereafter that you double charge me!