Constant flickering of screen

I have been a die hard SONY fan since they were partnered with Ericsson to this date that I am typing this complaint. <br> In December 2015 I have updated my Sony xperia Z ultra(C6833) from Kit Kat 4.4.4 lollipop to lollipop 5.1.1, ever since the phone's screen is flicker like Sony designed it just to do that. I've tried to get help in so many ways available, [URL Removed] , Sony twitter page, ZA Facebook page , XDA forums and even emailed the developers world team but nothing.<br> <br> The only thing we wanted was for you to make an update that's going to fix the bug that makes the Z ultra to flicker. I have read so many threads on the internet where so many people are experiencing the very same thing as me. <br> <br> In a nutshell, close shop because you are USELESS we'll use Samsung ,Huawei, HTC or other brands that give full support to their client.<br> <br> Bye sony