Open the Phone app
Tap Voicemail
Check if your carrier supports voicemail deactivation
Contact your carrier and request voicemail to be turned off
Ask your carrier to disable voicemail forwarding
If needed, dial your carrier’s voicemail deactivation code
Turn off Call Forwarding in Settings
Go to Settings
Tap Phone
Tap Call Forwarding
Turn Call Forwarding off
Disable Live Voicemail if available
Go to Settings
Tap Phone
Tap Live Voicemail
Turn Live Voicemail off
Restart your iPhone after changes are made