Unfair billing

Good day, I have serious concerns when it comes to billing... My account has been not more than R650 every month with my Samsung S4 mini, so I used my old blackberry, which I cannot even access internet on because it is a contract simcard and not a prepaid simcard to load blackberry data. So for the last two months I receive accounts for over the R1500.00 sms/ they charge me R600 for 600mb used???? seriously? is this fair? I did not even use my phone during June because its blocked then I get an account over R600.00? My monthly subscription has also increased now? Is it not a 24 month contract?? Can I report this to the ombudsman? I do not feel that it is fare to pay this for stuff I did not even use!! After numerous emails they just confirm my account is right! I cant see that it is... Help!!! Ombudsman? Cancel my contract? What to do??? <br>