MTN admit ***** to be credited and then decline cr

I have had very strange billing on my MTN data card since March 2013. Been querying from March 2013, no assistance. I kept paying anyway to prevent disconnection.<br> Sep 2014 my billing of R419 shoots up to R2900, eventually they report calls made on a sim I have no ownership of. I queried for months asking for answers, they investigated after I had been calling weekly for response, I get an email confirmation that ***** has been detected and credit will be passed.<br> In Jan 2015 after again pleading for answers and when credit will be passed, I am told I am responsible for the account but MTN will goodwill me for R2900? why goodwill me and not credit the complete ***** amount? They to this date have not passed a credit, rep**** to why billing was so inconsistent and now after numerous times have disconnected my phone due to outstanding account which to date they still have not rep**** solutions, answers or any credits. this means I am unable to make any calls working from my phone, due to their incompetence and lack of service.