Early termination fee *******ly charged

I have sent two e-mails to MTN Customer Service relating to a contract which had expired and I chose not to renew but rather migrate to prepaid. I received a statement and invoice advising that there was an early termination charge of R584 even though this is not the case and the contact I originally spoke to advised that I ignore the charge. The e-mails to MTN Customer Service asked for clarification but even though they have "Read" the mails per my read receipts (31 August and 04 September respectively) they have not bothered to respond. I would hate for my name to be blacklisted because of a fee that should in the first place not have been charged.