Screen unresponsive and my power button doesn't work

I tried to facetime my friend but my phone screen froze and then when they tried to call back my phone completely froze and now I can unlock it and see my home screen but I can't actually access any apps and my power button doesn't work. My phone was perfectly fine up until the call. Is there another way to shut it off or something else I can do?

[Re-Titled by Moderator]