Refund

I have taken a contract with MTN for R399 on a month to month. This January they deducted R2949. I queried and was advised because the debit bounced which was not true. They stated I can choose to have the money refunded to my bank account or Mtn account. I chose my bank account and they requested for my bank statement to show the money was indeed deducted. Every time I follow up on the refund I am told to resend documents. I keep on doing that and being given new case numbers every time I call. The experience has been nothing but frustrating and some of the agents are so non-chalant about it