MTN Overcharge

I cantacted MTN on numerous occasions; I also sent emails to ICASA regarding continuous overcharges on my contract. To date MTN has not credited my account and they still invoicing me the full amount. My debit order should be for the amount of R 369 per month. In November I was debited R 706.52 and December R 556.52. kindly assist me. My cell phone number is ***.