To change your voicemail password, you must know your current voicemail password. To access your device’s phone menu, tap the Phone tile. Note: If you have forgotten your existing voicemail password, you will not be able to access Voicemail until you reset your voicemail password.
Tap the Menu icon.
Access your voicemail by tapping Call voicemail.
Once connected, enter your current voicemail password if prompted, then press the 4 key > 2 key > 1 key > 1 key.