Phone is on the FaceTime ending screen and it won't reboot or turn off

Have you tried a forced restart?

It would be better if you can please post a screenshot, in order to understand the phenomenon better.

If an app unexpectedly quits, stops responding, or won’t open

If an app on your iPhone, iPad, iPod touch, Apple Watch, or Apple TV stops responding, follow these steps to get help.

Force quit the app

• iPhone, iPad, iPod touch: Close the app and open it again.
• Apple Watch: With the app open, press and hold the side button to show the power options. Then press and hold the Digital Crown to quit the app.
• Apple TV: Double press the TV/Home button and swipe left or right to find the app with the issue. Then swipe up to close the app.

Restart your device

Restart your iOS device, Apple Watch, or Apple TV. Then open the app to see if it works as expected.

Check for updates

Make sure that your device has the latest version of iOS, watchOS, or tvOS.

Then check for app updates. For iOS and Apple Watch apps, go to the App Store on your iOS device, then tap Updates. If an update is available, tap Update. If asked, enter your Apple ID and password. You might need a Wi-Fi connection to update some apps on your iOS device.

On your Apple TV, go to Settings > Apps and turn on Automatically Update Apps. If you don't have automatic updates turned on, you can open the App Store, go to the Purchased tab, and open an app's product page to see if an update is available.

Delete and reinstall the app

• iPhone, iPad, iPod touch: Delete the app, then redownload it from the App Store.
• Apple TV: Highlight the app on the Home screen, then press and hold the Touch surface until the app jiggles. Press Play/Pause, then select Delete. Open the App Store and redownload the app. Some apps require subscriptions for activation. If you can't activate the app or you don’t remember your sign-in information, contact the app developer.
• Apple Watch: Open the Watch app on your iPhone and tap the My Watch tab. Scroll to the app you want to remove, then tap it. Turn off Show App on Apple Watch, and wait for it to disappear from your watch's Home screen. To reinstall the app, scroll down to Available Apps in the My Watch tab and tap Install.

Contact the app developer

If you're having an issue with an Apple app, contact Apple Support. If it's a third-party app, contact the app developer.

Learn more

Get help with unfamiliar charges and in-app purchases.

If you can’t install or update an app, or if it’s stuck waiting, learn what to do.

Get help with audio, video, or power on Apple TV.

If an app unexpectedly quits, stops responding, or won't open - Apple ...

https://support.apple.com/en-us/HT201398