Q: iPhone 6s 64 gigs ends calls when I lock the screen and is buggy

Howdy Dr3es,

It sounds like your phone calls end unexpectedly when you press the Sleep/Wake button and when you go to unlock the phone with Touch ID the top bar that shows your carrier and battery charged percent is missing for a few seconds. I would start by quitting all the running apps first:

Force an app to close in iOS

1. Press the Home button two times quickly. You'll see small previews of your recently used apps.
2. Swipe left to find the app you want to close.
3. Swipe up on the app's preview to close it.

When you have done that restart the device and test the issue again:

iOS: Turning off and on (restarting) and resetting
 
If the issue persists, backup your device to iTunes, then restore it as new and verify that it works. 
 
How to erase your iOS device and then set it up as a new device or restore it from backup

If it does, then restore your backup to either verify it still works and the software just needed reinstalled, or isolate the issue to the backup file itself. Thank you for using Apple Support Communities.