Disputed Billing - Charged for data not used.

My query started in 15mnths ago, charged for data not utilised, queried with Billing, spoke to a Veronica, charge was reversed, however data billing continued, requested an investigation it was mentioned that my dual sim was being utilised in a modem however my sim was used in my tablet.After many communication with dept I requested to have my line closed and kept open for incoming,to prove that I was not using my phone. Weirdly enough data was still being charged via my dual sim which by now had been confirmed blocked by MTN. Requested full investigation, I then refused to pay for an account which I had not used. I was then handed over to attorneys, paid the bill. As per Attorneys I am fully paid, contacted MTN they now said I still have outstanding amount, even your Attorneys are now confused...what is happening, you have internal ***** happening in your company. My mobile ***, How is it possible that a blocked sim can generate data?????Will be taking my case to the Ombudsman, this is unacceptable!!!!!!