Non delivery of cell phone

On the 26th September 2014 a lady called Primrose phoned me from Mtn to upgrade my current contract with Mtn. I agreed and was promised a new cell phone to be delivered at my residential address in Thabazimbi. The unit was not delivered and I phoned numerous times to the call centre on the 30th October,7th November and 26th November talking to Primrose, Ketumetse and others, to no avail. On the 22 July 2015 I visited the Mtn branch at Rustenburg where the lady phoned the call centre again for me and I was promised again Mtn will contact me to sort out the problem, again no phone call from Mtn. By now I want to cancel my contract with Mtn as they did not keep to their contract obligation. Is it possible that you can help me cancel this contract as the 24 month will now only expire in September 2016