Assist from Mtn contract

I subscribed for 35GB for R265.00 but they deducted a lot of money from my bank account recently this month they deducted almost R770.00 or something and I had subscribed for a data of 10GB with my old SIM card then I upgraded to 35GB for the above mentioned fee , when I enquire about the abnormal deductions they said I had app**** for business what what and they keep deducting for what I did not agree for, they said they had fixed my problems but it doesn't seems like that,if they don't return all the monies they took from me they rather cancel everything Please assist me My ID *** My Contact ***Kindly Mr L.M. Mo***eng