Attention! If you have seen a flickering gray bar at the top of your iPhone 6 or iPhone 6 Plus, this could be a serious problem. Many customers reported seeing the gray bar followed by a frozen screen where the touchscreen stops working. There have been several complaints and this has been a serious issue for the Apple repair technicians.
You can try twisting the phone a bit or putting pressure on the screen but if nothing seems to work, then the problem lies with the Touch IC chips in the phone. These must be replaced for the problem to go away but Apple is not equipped for that work.
Although the issue is still looming, Apple technicians and researchers are doing their best to find an answer until Apple officially endorses a solution. Until then, customers may just have to get a new iPhone.