Locate then select the appropriate app.
If system apps aren't visible, tap the Menu icon (upper-right) > Show system.
If troubleshooting for Voicemail, tap the Phone app then follow steps 5-9. Once reset, you must activate Voicemail.
Tap Force stop.
Tap Storage & cache.
Tap Clear storage.
This option may not be available for some apps.
Resetting an app does not remove saved items on the device (texts, pictures, voicemails, etc.); however, saved passwords for Wi-Fi, settings, backgrounds, etc. within the app itself may be reset.