Cancelation Nightmare

I have been trying to get ahold of the cancelation department for 2 months to cancel one of my contracts with MTN but no response. I have contacted 135 multiple times a day and NEVER get through to an agent. I have sent e-mails with no response. I am being billed for a device that I have paid for the 2 years. Utterly disgusted and feel like canceling all my contracts with them!!