No notification of using up the data bundle

I have had a MTN internet contract for a number of years. Today I checked my bank account in order to identify why I have gone into overdraft. To my shock I discovered that MTN has deducted almost R2000 from my account for my internet contract. The standard rate is R89. <br> <br> I have never received a notification that I have used up my allocated bundle and that I will now be charged at out of bundle rates. I find this completely unacceptable as I would expect a notification as my 3G ****le does not allow me to check my balance myself. <br> This is not the first time that it has happened and I feel that it would be better for me to cancel the contract and move to Afrihost or Cell C rather than stay with MTN. <br> I have tried phoning the customer care line however I am disconnected the whole time. <br>