MTN it's over and I want my money back

I canceled my contract with MTN after the contract period expired they then debited my account after the contract period ended. To resolve this matter I have been calling their customer care line following all the prompts to speak to a consultant to which all of my phone calls were dropped. I canceled my contract with MTN because of the poor reception on their network in my area as well as what I believe is unfair conduct by increasing my contract amount due to the company's economic hardship as I don't want a rely on a company that has poor service and struggling financially to provide this kind of service to me. I am now unable to contact MTN to explain to me why they are entitled to debit my account as well as ensure that our business relationship comes to an end. I hope someone can advise me on how I can end this abuse and be free from this ************ company?