Apple - iPhone - How To - Phone - Receiving Calls

Receiving Calls

When you receive a call, tap Answer. If iPhone is locked, drag the slider. You can also press the center button on your iPhone headset or the equivalent button on your Bluetooth headset to answer a call.

The stereo headset, with a callout showing the location of the center button in the cord going to the right ear piece.

Silence a call:

Press the Sleep/Wake button or either volume button. You can still answer the call after silencing it, until it goes to voicemail.

Decline a call:

Do one of the following to send a call directly to voicemail.

Press the Sleep/Wake button twice quickly.
Press and hold the center button on the iPhone headset (or the equivalent button on your Bluetooth headset) for about two seconds. Two low beeps confirm that the call was declined.
Tap Decline (if iPhone is awake when a call comes in).

Block calls and maintain Wi-Fi access to the Internet:

In Settings, turn on Airplane Mode, then tap Wi-Fi to turn it on.