Just Uninstall the COMPASS, and restart the phone, it WORKS,
I have same problem with that when i upgrade my phone into 11.4.1 My old phone only 16gb storage so im struggle to install a new upgraded IOS. So i decide to uninstall or they called offload or delete app some software that i did not use. When i finish to upgrade it and cameback to install the software like notes, tips, compass, podcass, itunestore etc. first was i install the compass, when the compass install i restart the phone, and then boom I notice that my screen came to black or become auto off when i touch nearly top left of the screen. I wondering why, i ask some of my officemate what happen? They say screen damge or software problem. Etc. I search the net says it is sensors for some case, it said base it on upgrade system in call senario, when someone call you or you call, the screen auto turn it off. Using the sensors like a orange dot in top of the screen. I notice something for it and yup it is true the sensors was to much sensitivity maybe because of some bugs for updates. I found that so if this a sensor i need to find how off this BAD THINGS. And boom i realize i need to uninstall some app that had also a sensor. Fast forward. I uninstall the Compass using this menu. Go to General Setting, Iphone Storage, find compass there, click it, choose to offload it or delete it (uninstall). Then restart the phone. And yup it works. 100x touch the orange dot sensors at the top of screen, never seen the screen turn it off again. By the way i using old phone just IP5s nothing else. I hope it work for your phone. BOOM