How to Use the Speaker When Checking Voicemail on an iPhoneby Heather Harris
When you want to listen to the voicemail messages on your iPhone, you may not want or have immediate access to a pair of headphones. There's no need to worry, however, as you can easily listen to those messages from the speakers built in to the iPhone's hardware. With just a few taps of your finger, your messages will play out loud with nothing to plug in and no cords to get tangled up.
Tap the "Phone" icon on your iPhone's desktop.
Tap the "Voicemail" icon in the Phone menu.
Touch the "Speaker" button, then select the message you want to listen to.
Adjust the volume with the hard buttons on the side of the iPhone.