MTN Debt collector overcharged me by R7,614.29

MTN Debt collector overcharged me by R7,614.29. I called them the first time and they told me to send an email, I sent an email and it just fell through the cracks I guess. I called them again on October 16 explained my problems to Clarance Mdima she also asked me to send her an email so I did. I sent her about 3 follow up emails thereafter there was still no response. Sat the 26th of October I called again only to find my query is still not logged and the person said nothing other than to keep sending Clarance email. THIS A LOT OF MONEY MTN!!!!! and I'm disappointed by your service.