Cracks at the back cover

<p>I bought a Sony Z5 2 months later the phone starts cracking at the back cover ( it didn't fall, i thought maybe I bumped in to some thing) I bought a cover 2 weeks later I see more cracks(8) the phone never fell since I bought the cover. This is just disappointing because Sony doesn't wanna explain why the back cover cracks, i would understand if it was the front screen. I ordered the phone from vodacom online. Sony says I must take it up with my service provider. Vodacom didn't design the phone Sony did.</p>