Billed sky high for a top up package

I am Disgusted with the billing system and how Cell C just bills me for errors made my their staff members.<br> I ask to be loaded on a 2gig top up then I get loaded on a 3 gig. Cell c never cancelled my BB plan after upgrading to a LG G3. Then my account is R857.74 this month. NOOOOO this is so not on.<br> I refuse to pay for errors that someone else has made. I work hard for my money! I would like this matter sorted out ASAP if not done and corrected I will cancel my contract from Cell c immediately.