Billing Nightmare

I took my 3G data contract with Autopage in 2010.It was 500mb & when the limit was reached I buy airtime & top up.I have internet at work therefore my limit was seldom reached. In 2014 I was contacted to say I am paying too much & it can be upgraded to 1GB & the monthly charge would be R69.99,over R100 saving. I agreed to the upgrade.<br> In August 2014 I received a bill for over R1000.I called & also logged a query on the Autopage website to alert them to the problem.Then in September I received a bill of over R8500.I was then sent a letter stating they had billing problems over the last 5 months.I called again & submitted a URL request form in December.The first response to numerous queries was a Legal letter in March 2015. Again I called & asked for feedback on my query. <br> It's been 11 months since I first logged a query & now I receive the next response to state I am now listed on the ITC.There is no way I could have used over 20GB in 2 months.I was on a top up account to my knowledge & at 1GB it should have cut off.I have made numerous calls,been to the local branch,logged complaints on the website & sent emails, & I have had no feedback to my query.