MTN call center that cannot assist

I have been trying to cancel the contract for more than 3 weeks, I called their call centre number which is 135 and everytime when their consultants are putting me through it gets cut off immediately, I was told to call *** when it cuts off and that number says it does not exist, To my shock I went to the MTN outlet in Quagga centre where the guy tried to assist me and he experienced the same thing, where he told the call centre people that the number they kept giving to me was non existent. I wonder how does such a big company be so unprofessional in giving services. I am so bored and I don't think I am ready to continue with their services.