Open the Phone app
Tap Voicemail
If your carrier supports Visual Voicemail deactivation, contact your carrier and request voicemail cancellation
Dial your carrier’s voicemail service number and follow the prompts to turn off voicemail
Ask your carrier to remove voicemail from your line entirely
If you only want to stop voicemail notifications, go to Settings
Tap Notifications
Tap Phone
Turn off Allow Notifications
If you want to disable voicemail forwarding, contact your carrier and ask them to remove conditional call forwarding
Restart your iPhone after the carrier changes are made