Another cracked screen

I am once again having to deal with the incompetence of Vodacom and their repair center. Last year my Sony Experia V's screen cracked when the phone over-heated. After 2 months of fighting, the phone was eventually fixed and returned to me. On 26 March the phone's screen cracked again. I was holding the phone, it over-heated, I put it on my lap and the screen cracked in the exact same place. The Manager at the Tyger Valley branch was completely rude to me when I took it and explained my frustrations. And now, once again Vodacom is telling me it is due to physical damage. Firstly, I wouldn't lie about damaging my phone. Secondly, this is the 2nd time this is happening. Thirdly the phone has a Gorilla screen, so please tell me how is cracks?!?! I DO NOT want my phone back, I WILL NOT be paying for it to be fixed, and I want a brand new phone in its place. Seriously Vodacom, its time to come to the party and fix this mess up! If this is not sorted out, I will be going public with this, including the newpapers and Carte Blanche.