Can I leave the call screen without ending the call?

Yes. Tap the arrow at the top left or press Back, and the call carries on as a small round bubble with your AI character’s picture and the time left. Drag the bubble anywhere. When you let go, it moves to the left or right edge of the screen, whichever is closer. Tap it to go back to the call. Only the red End button ends the call, and switching to another app ends it too.