Write an article based on this "Access your voicemails. Tap a message you wish to open. Tap . Tap Delete to delete messages. Tap Call Back to dial the number that left the message."
As long as your carrier supports visual voicemail, you can access your voicemails by tapping the Voicemail button in the bottom right corner of the Phone app's screen. You will be able to browse through all of your voicemails and choose which ones you want to listen to. Some carriers' data plans won't allow you to view your voicemails; instead, you'll need to tap and hold 1 in the keypad or tap the Voicemail button to call your voicemail inbox. Doing so should bring the message up in a window that includes several options like Delete and Call Back. If your iPhone supports visual voicemail messages, opening a voicemail message will display a transcript of the message's content. It's in the bottom left corner of the voicemail message you opened, directly above the Speaker option. Tapping this will begin playing your voicemail message. Tapping Speaker will play the voicemail message over your iPhone's speaker. The Delete button is in the bottom right corner of the message window. To delete multiple messages, tap Edit in the top right corner of the screen, tap each message you want to delete, and then tap Delete in the bottom right corner of the screen. It's at the center of the bottom of the voicemail message window. You can see how many new messages you have by looking at the little red number on your Voicemail icon.