Hello there, cctbeef.
It seems you have come from the Knowledge Base article that has the steps you need to try for resolving your exact issue:
Follow these steps to troubleshoot voicemail issues on your iPhone:
- Restart your iPhone.
- Check for a carrier settings update.
- Update your iPhone to the latest version of iOS.
- Ensure that your voice mailbox is set up properly. You can verify this by dialing your phone number from your iPhone.
- Make sure that you have a good cellular network connection. You can verify this by seeing whether you can make an outgoing call.
- Call your iPhone from another phone and attempt to leave yourself a voicemail.
- Reset your network settings by tapping Settings > General > Reset > Reset Network Settings.
- Contact your carrier and ensure your iPhone is properly configured with the voicemail feature on your plan.
Thanks for reaching out to Apple Support Communities.