Contract upgrade

After waiting for 3 hours on 2015-07-06, I finally managed to get am upgrade on my cellphone contract but to my disgust, the upgrade have not been effected to date 2015-07-09. The new sim card does not pick up the network. I have tried numerous times to contact their call-center having to hold for about 36 minutes without any response and having my other calls cut off. I am really frustrated as I cannot use my phone nor access the services which I pay for. Mtn is such a bad provider, I want to know what my options are? Is it possible to cancel the contract and move to better service providers? I really feel hard done by mtn after being with them for over 2 decades. I hope their service leads to the loss of their valuable customers. Mtn sucks!!!!!