Billing query not dealt with

Twice earlier this month I submit queries on Autopage's website which were not satisfactorily answered. I was billed about R500 more for December than usual which was shown as data on the bill, however, from the time I received notice that the data had run out, and leaving the country early the next morning, 2.5GBs of data was billed, which is definitely incorrect. I need an explanation on this. I also asked when my contract expires and how much I am paying per month for my device, which was not answered. At the end of the contract, I need to understand how much the monthly bill will fall by?