Data charges on bill are unjustified.

I have gone to the MTN store in Umhlanga, Durban in May and queried my data charges. I buy data every month for and get constant reminders when the data is running out. I was shocked to see more data charges and have requested that I be provided with the itemised bills from May 2015 to date and no one has sent them to be. I told them I am unable to access the bills that are sent to me via e-mail. I need to scrutinise the bills as I have been overcharged this whole time. I have been buying data every month and get the sms's that it has been loaded. Despite this I get exorbitant data bills. Some lady from the call centre called me and said I owed MTN despite me giving the store proof. I want this matter resolved so I can port my number as MTN has been treating me badly of late. They even listed me for a second number that my Mom was using and unfortunately passed away and are busy with her estate and I neglected the number and has since been switched off. I made attempts to contact them and nothing only to get a shock when I saw my credit report. Being with MTN for decades this treatment is unbecoming for one of their loyal customers. They will lose 8 subscribers.