iPhone touch screen not working

Hi - my son's iPhone's touch screen suddenly stopped working last night, which means it is basically unusable. We've already removed the protective case, cleaned it the screen, restarted it, turned it off and let it sit overnight, but no luck. Before taking a trip to the Apple store - has anybody faced this problem and have any suggestions? Thanks.

is it a iPhone 6? There is a known issue but I'm not sure how Apple is handling it. Apparently some if the wires come loose or break inside the phone Go to a Genius bar

This happened to me this weekend. Hold the button on the side and the round one on the bottom-front at the same time until the apple appears. I think it is called a soft reset.