To change your voicemail password, you must know your current voicemail password. Note: If you have forgotten your existing voicemail password, you will not be able to access Voicemail until you reset your voicemail password.
From the home screen, tap the Phone icon.
Tap the Visual Voicemail icon.
Tap the More icon.
Tap Change password.
Enter your old and new desired password, then tap the Return icon.
Re-enter the desired password to confirm, then tap OK.