Turning on Do Not Disturb

Still getting interruptions?

Android (10 and above)
Quick setup - Swipe down from the top of your screen to open the notification center and tap the Do Not Disturb (DND) icon. 
Other settings - Press and hold on the DND icon to go to its settings (or go to Settings > Sound & Notification > Do Not Disturb) and you can adjust the behavior (do you want silence or vibration), the exceptions (do you want to allow calls from certain people), and the schedule (set the times you want to be on DND).

IOS:
Quick setup - Open control center by swiping up (iPhone 8 and earlier) or by swiping down (iPhone X and later), then tap the Do Not Disturb icon. 
Other settings - Press and hold the DND icon to go to its settings (or go to Settings > Do Not Disturb) and choose when to silence calls and notifications, who to allow calls from, and if you want to allow repeated calls to go through.