After pressing the Voicemail tab, all of the voicemails stored on your device will display. From here, you’re going to want to tapGreeting located in the top left. There will be two options located on the Greeting page: One option to utilize the default voicemail message and another to record a custom message.
Password: Make a note of your voicemail password—you will need this password to access your voicemail messages by phone. Also, you can reset your voicemail password at any time by clicking Reset Password. Set voicemail notification settings if you want to be notified when there is a new message (Enable Message Waiting Indicator), or have your

My iPhone Won’t Play Voicemails! Here’s The Real Fix For Verizon, AT&T, & T-Mobile.
After setting the number on your voicemail, you must also record a personal voicemail greeting. Follow the steps below. Start the Phone app. if you don’t see the numeric keypad, tap “Keypad” at the bottom of the screen. Tap and hold the “1” for about two seconds until the phone automatically calls voicemail. Immediately tap “3” to access voicemail settings. Listen to the options. On most voicemail systems, tap “2” to start the process to record a new greeting. The current personal greeting will play; then tap “2” again to record a new greeting. Say the greeting you want, and tap “#” when you’re done. To save the greeting, tap “1.” The personal voicemail greeting has been set. Hangup the phone. How to setup voicemail using a Visual Voicemail Applications