I have the same problem. It has frozen from messaging apps, google chrome, the home screen, camera and just about any app I've been using. I have to hard reset every time. If turn off the screen, it won't turn back on without the hard reset.
I've been a little concerned about this.
Had this phone since September 19th, though the first time it happened was last week.
The phone works fine after a hard reset.
I just came from the Apple Store, I simply told them I wanted to return it, cause if you tell them there is an issue they'll give you a refurbished one from the back, and after paying full price I don't think so. So I returned it now and bought another new one, no questions asked. Good luck