Sony Xperia Z3 overheats and cracks

On 29 Dec 2014 I upgraded my Vodacom contract and got a Sony Xperia Z3. On 5 Jan 2015 the phone cracked from overheating and became useless. I returned it to Vodacom and waited. A week later I contacted Vodacom only to be told that they did try to phone me but I never answer my phone. I had no missed calls on my Vodacom contract phone that week and I am the only person who uses the phone. They told me that the phone couldn't have cracked on it's own and that they must send it to the manufacturer for evaluation. That was the last I heard from them and now it has been almost a month.