Phone only used for 2 months

I signed a contract with Chats Woodmead for a Sony M2 Aqua in March 2015. The phone has only worked for 2 months. The first time, it switched off and never switched back on again. I returned the phone to Chats Woodmead who sent it to Vodacom to be repaired. The repair took 4 weeks and the problem was diagnosed as a software problem. The phone only worked for 6 hours and switched off again. The problem was diagnosed as the same. Vodacom refuses to give me a new phone. How do you expect me to pay a contract where I am not utilising the product? In terms of the CPA, I am as a consumer entitled to a new device if the device breaks for the second time. My phone cannot constantly be repaired and I never get to use it. How is that fair to me as a consumer? My IMEI number is *** and repair number is ***2. Vodacom, you need to replace this device as it is an inferior product with numerous technical problems. I expect a response