Tap Speaker .
The light bar on the Speaker button illuminates blue to indicate that the speakerphone is on and the sound from your call is played through the phone’s speaker on the back of the device.
While viewing the in-call screen, you can turn the speakerphone off by tapping Speaker again.
The speaker is turned off automatically when the call ends.
To avoid damage to your hearing, do not hold the phone against your ear when the speakerphone is turned on.