MTN won't cancel my contract

I opened an data Sim only contract in August the consultant who assisted me **** and said there's coverage in my area which is not true. I called to be assisted coz I would connect and say no internet connection.can cancel it because they want to debit me for something I don't use. They say there is an error when calculating my early cancelation fee so they can't see how much I should pay this was in September even now. On LinkedIn they always say sorry we are still waiting for feedback every day for weeks now when I call they open a ticket will their technician to assess the error as soon as the call ends I get an sms saying your ticket has been resolved. I call the following day to get follow up they say we will call you no call back. Worst case scenario they will debit the money for a service you're not getting. Please cancel my contract MTN