iPhone 6s freezes up w/iOS 10

I downloaded and installed iOS 10 my iPhone 6s and now my email and Message apps freeze up while I'm attempting to respond to an email or type a message. I went to the Apple Store and they first attempted to reset the phone and reinstall iOS 10 with the same end result. They gave me a new iPhone 6s and it is acting up, just like the phone that I exchanged. How do I get iOS 10 to play nice with my phone?