MTN billing data to my account that I did not use

I received a bill in September 2017 for over R2 000 for data on an external usb ****le, that has not been used for a long time. These charges started in August 2017. It was during the week, odd times like 22:49; 04:55, right through the day (while I was at work)... I moved and had Wi-Fi for a long time and that was why I stopped using the data card. But they kept charging me excessive rates out and about my normal contract amount of about R99.00. I inquired this with MTN and they kept on saying, even after I submitted an affidavit to them confirming that this data card has been put away (in drawer where no one had access to), that I am liable for the cost. They cut me off on both my numbers on this contract and I told them that I am still refusing to pay since I did not use that data. After one month they reconnected me and ever since I have only been paying my normal monthly installment to them for both contracts on my name. When I wanted to upgrade about a week ago, they told me that I cant. I told them to cancel both these numbers then, and they told my they cant. This data has not been used by me, and MTN have many cases like this when numbers have been handed out or mixed up that has not been used for a long time. And then I get charged for the data?! I need MTN to sort this out, I want to get this amount cleared from their legal department against my name and they can cancel my contract with them. I will never support a company like MTN again after wanting to ***** from me and then refusing to sort this matter out. I need a solution from MTN asap!