MTN SHOCKING DOUBLE BILLING AND POOR CUSTOMER SERVICE

Last month I received an increased amount on my debit order,in fact it was double the amount, I immediately called the call centre to inquire about how this happened when I have not been contacted about it. She did not have an answer for me and logged a call and advised that I will be contacted in three days for feedback. To date nobody has bothered to call me and I have been billed once again.This is shocking customer SERVICE and I want answers