My iPhone 6 appears to have a touch screen issue. It will open an app I am not touching, or the screen will move rapidly when I do touch it, then it will open something I am not intending to open. What is causing this?

iPhone 6 - touch screen appears to have an issue. I can touch one app, but it will open another app that is not even adjacent to the one I am attempting to open. Plus, I can try to open a text message from one person, but it will jump up or down several texts and open one from someone else. When typing, sometimes it will type letters when my fingers are hovering above the keyboard and not even touching, or it will type letters different from the ones I am touching. Any ideas what is causing this? The phone was purchased new from AT&T Store in January 2015. Software is up to date. Thanks.