Incorrect Billing

In September 2014, i went to Faerie Branch and changed my contract into top up 200 . That is for all the numbers in the contract except for a 5 gig data one. Autopage sent me SMS immediately saying that i changed contract into top up 500 . Within 2 minutes the sent another SMS indicating that was a mistake . They later sent another SMS confirming that all the numbers in that account has been changed to Top up 200 . On the 17th of each month they send an SMS indicating that they topped up the 200 and 25 free SMSes . To my surprise i received an invoice that i was owing them R 14000-00 in January 2015 . I called the Head Office and spoke to the person handling the account . She was very rude but later they called to say they have rectified the account . Then the end of February same thing . I called them again , but no one could assist , instead i was threatened with legal action . Now, on the 11th May i was called by their legal department about the account. I explained to her what the problem is, she requested me to send her the email of which i did . She promised to come back to me, up to this point nothing . On the 13th i called, still promises that they will call back, nothing