PACKET SWITCH DATA CALLS

I received my MTN statement on the 24 August 2015 and was shocked to see a data bill charge of R 1574.77 on my account. This is a HUGE shock as I only use the USB ****le to check my emails in the evening which takes about 10mins. before I received my statement I noticed that i was unable to check my data balance and during the same time i called MTN to check why my everyday cell phone sim was deactivated and they advised that it was a tech error on their end so i assume the error has messed my my data sim or my entire contract in some crazy way. Now I have logged an inquiry with MTN via the call centre (***) & this will take 2-7working days. This is unacceptable as my debit order will go off on Friday and they will take the amount they claim I owe before they even investigate my issue. I have advised them that I will be stopping their debit order while I await feedback on my issue and I will be getting an affidavit at the police station stating why I am withholding payment. I do this because I do not want them to take the HUGE amount (Which I cant afford!) and then if they find its their problem they will credit my account and I would want a refund which they do not offer