Incorrect Billing

My bill for my cellphone has constantly been between R800 and R1200 since joining MTN which are fairly normal and when comparing to other networks seem competitive. <br> <br> At the end of May 2015 I was a debited roughly R4500 which seemed exceptionally high but I Paid the bill and immediately called the call center asked for an itemised bill and a limit to be set on my account. Again at the end of June I was debited with R4427,86 this was very upsetting because I have data bundles loaded and a limit on my spending, so I asked nedbank to Reverse the debit order which they did. I have called Paulo at MTN Hyde Park who is great but I feel can only be a messenger in this instance so I called the MTN call centre numerous times, when I could get through (which is seldom) I end up speaking to people who cannot help me and can acknowledge that there is a limit on the account but cannot tell me why my bill is so high, I have requested numerous invoices/itemised bills but still havn't received a thing. I ended up doing an EFT payment as my account got suspended it was then restored back and now it has been suspended again and the call centre cannot take calls.