Contract Airtime Dissapeared?

I am on a top R350 contract for a while now through Autopage with MTN. <br> <br> I never get to the end of my airtime ever and usually have between R700- R900 airtme at any time due to never using it and the carry over. All of a sudden now my airtime balance is R0.49c and i have not made calls for that amount or anything. I call autopage and then cannot tell me what the story is. I have to wait 4 days to find out why now, my airtime is finished. there is no way to see on the system where or how it was used? <br> <br> I would like clarity on how this is possible? and why i need to wait 4 days... how do i make calls for the next four day without BUYING airtime... this is why i Have a contract? <br> <br>