Hey there revDAVE,
It sounds like your voicemails are returning a day or so after deleting them. I recommend these steps specifically from the article named:
iPhone: Troubleshooting voicemail
- Restart your iPhone.
- Check for a carrier settings update.
- Update your iPhone to the latest version of iOS.
- 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.
Thank you for using Apple Support Communities.
All the best,