No feedback on data dispute of R10000

I'm extremely disappointed and upset with this service provider. I have been a high usage user with my contract and always been happy until recently. Separate to my open contract line I pay an additional R99 for 500MB monthly and when the 500MB is done I just purchase more as the data will stop and notification will be sent it's run out. For the whole of last year it's been working excellently and I've been happy. Until when I got my bill last month indicating that for the month of Dec and January I ran a data bill of R10000!!!! Why for those 2months was the data allowed to run up like that? We went on using the data /phone without realizing that for the 2 months it was on 'open line' which I assume it was as how else could such an amount be accumulated if I pay separately for 500MB?!?! I raised the dispute 27th Jan and received smses as reference but no contact has yet to be made with me!!! Totally unacceptable service! I'm seriously considering changing networks and was even advised to go to a paper!!