Repeated refusal to assist with cancelling a contract

I have been trying to cancel a MTN contract due to the bad signal and non-existent customer service for almost 2 months now. Despite 2 different MTN agents assuring me I can just cancel it in store within 7 days if I am not happy, they refused to do so went I went back the next day. When I phone customer service they claim the number I was given does not exist in the system and refuse to help me. When I send an email it gets ignored, and once a week when I follow it up the email gets forwarded to someone else who then also ignores it. But when month en comes around suddenly I am on their system to pay for the contract they claim does not exist. I have never in my life had to deal with customer service this bad, taking out a contract with MTN was the worst decision I have ever made.