How can I fix my iPhone when apps keep crashing?

Whenever I try opening either imessage, facetime, or the phone app on my iphone, I just get a black screen for 10-15 seconds, and then it shuts down and reverts to the home page. I have tried restarting my phone multiple times but that has not worked. I have also tried to access the Settings app to try to solve the problem, but whenever I select imessage, facetime, or phone on the Settings app, my phone just freezes. Anyone know how to solve this?

[Re-Titled by Moderator]