It can be embarrassing if your phone rings when you’re in a meeting – even on silent, the phone’s vibration could still cause a disturbance.
Instant silence
To immediately silence your phone, simply tap the Side button on your device once.
Even if you silence a call, it will still seem like the phone is ringing to the caller, but your iPhone will now be silent and stop vibrating.
Send to Voicemail
Send an incoming call directly to voicemail by tapping the Side button twice. Beware that cutting the rings short in this way may make it obvious to the caller you are rejecting them!
If using wired Apple headphones, the same thing will happen if you press the central button twice on the headphone control.