Mtn Customer very bad service

I received my monthly account for my Internet on 17/08/2015 and noticed that MTN charged me R337.39 extra for using more data than my contract allowed.Because of the fact that my son make sure that he don't use more than allowed I know I am wrongly billed.I first tried to phone customer Care Enquieries in the moning.You can only phone with cell phone and I hold on for 45min and still nobody answered.I went to the MTN branch in Centurion and Mabandla said he can't give me a statement and have to send a report to checked my account to Customer Centre.Ref nr was REQ:***.He also gave me a land line number *** and said when they answered I must asked for Customer Care.Just for somebody to answered at *** took about 30 minutes and when she put me through another 40 minutes before Customer Care answer.They just said somebody will investigate and come back to me. REQ:***.TILL TODAY NOBODY COME BACK and MTN took extra money with my monthly debit order on 01/09/2015.THIS IS NO SERVICE AT ALL AND WHEN MY CONTRACT EXPIRE AT END OF DECEMBER I WILL CANCEL AND HOPE THAT I DON'T HAVE TO DEAL WITH MTN EVER AGAIN.Can somebody please come back to me !!!!!!