Crack on iPhone due to unproper fix

On the 31st march I went to iFix store in Melrose Arch to fix my Iphone 4 screen. I pay R749.00 for a new scress plus R200.00 for the express service. On Saturday, the 02nd April, a crack showed up, without an apparent reason. I've looked the screen and I saw a little space between the screen and the device, which means the screen was not well fixed and create the crack.<br> <br> I came back to the store on Sunday and I gave my contact details for further authorization from the manager. The authorization was processed and then I returned on Monday. At the store I was asked to sign a term where it said iFix won't fix the screen if a crack shows up again. I did so. At the end of a 2 hours waiting, the technician told me that the reason for the crack was the space left in the screen and he did something extra to avoind another crack.<br> <br> When I listened that I asked why I was asked to sign a term if the fault for the crack was not mine. Nobody reply and I left the store without a copy of the term.<br> <br> What happen now, legally, if that happen again? Where is the ethic on business?<br>