A nightmare with data contract

I had a data contract with MTN network and i was paying R314.19 for 24 months and when the contract matured they said I need to pay the last R314.19 so i can close the account. I couldn't afford to pay it that month and when i tried to call the customer care number, the phone kept being dropped and when i go to the branch they said they cant help me i need to call customer care(i went to different outlets). I finally managed to get hold of consultant last week and they sent the invoice.this is when i discovered I have been charged R1445 per month from February(which is the maturation month).I have not used the Sim card since February and when i ask about the huge bill all consultants drop the call. I reached out on twitter to try get the sim card activity since i havent used it since February but im still waiting, they told me that R1445 will keep on being added until i settle the amount, according to them I'm currently owing R 8858.69.this doesn't make sense as I was paying R314.19 per month and usually if you fail to pay for data they would switch off their data now they claim I owe this much amount of money and I haven't used their services!