Excessive billing on 3g internet !!!!

For some or other reason for the last 10 months my internet bill has been sky high.It will be high one month and then low as per normal.The last 2 months has been too much.First R3500 and the last one R2300!!My debit order did not go through,who has R3500 for cellfone!!!So this meant that I now owe them +-R6000 for the first of November!!This is insane,I don`t have that kind of money so now my cellfone line has also been suspended.I have spoken to Autopage(who are my service provider)but this was a dead end,no help came from them.I have a 2gig data plan and hardly use the stick,I have Wifi at work so al updates go through wifi for the computer,only sometimes we use it at home in the evening and then weekends.I have had the internet for +-18 months and before the last 10 months I have never had a problem.Something must be wrong!!So if someone can please help me out with this,I need my fone!!!!I can only be reached by [Email Removed] or the office***) as my line has