Pathetic service and unauthorized debit orders

MFC had debited my bank account for my vehicle finance in May for more than R2000 more than what should have been debited After complaining to 4 of the call centre agents who called me to demand payment, I spoke to a manager Zinia Mariba. She admitted that it was a mistake and that the balloon payment had accidentally been added to my debit order. She asked me to do an EFT for the normal amount, which I did the same day. I asked for a letter explaining this and a refund of my bank charges. I sent through my bank statement as requested and to date, have not heard back from Nedbank, yet I am receiving final demand sms's asking for payment. I received a letter which strategically cut off her email address so that I can't contact her. I want my bank charges refunded and this error must be corrected.