iphone xr is frozen on facetime call ending, can't ACCESS ANY APPS.

You need to reset your device:

• On an iPhone 8 or later: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then press and hold the Side button until you see the Apple logo.

You may have to repeat these steps multiple times to get the device to reset.

Best,

GB

And you have also tried to force close the app:

Force close an app

1. On an iPhone X or later or an iPad with iOS 12, from the Home
2. screen, swipe up from the bottom of the screen and pause slightly in the
3. middle of the screen. On an iPhone 8 or earlier, double-click the Home
4. button to show your most recently used apps
5. Swipe right or left to find the app that you want to close.  
6. Swipe up on the app's preview to close the app. 

When your recently used apps appear, the apps aren’t open, but they're in standby mode to help you navigate and multitask. You should force an app to close only if it’s unresponsive.

If you have already also tried that, then you will need to visit your local Apple Store to get help.

Best,

GB