Edge protection insufficient

Although the cell phone fits perfectly in the shell, but unfortunately I find the edge protectors at the top of insufficient. The margin is too low and the cover slips already at a slight fall (from a low altitude) away to the side. This my phone has been a slight damage to the edge.

Addendum:
Even if the shell has not met my expectations, the service of Mumbi is recommended and the Fa. Is very interested in customer satisfaction!
I got completely refunded the purchase price, plus get even 2 Pck. Screen protectors.