Option 1: Set Your Phone to Airplane Mode
This is one of the more helpful solutions for “iPhone won't delete voicemail” issue. Many users have succeeded in deleting voicemails via this method. The method is quite simple as all you have to do is set your phone to Airplane mode. Follow these instructions:
- On your iPhone's Home Screen, swipe up from the bottom if you have an iPhone 8 or earlier ...swipe down from the top right if you have an iPhone X or later. A new control center window will appear.
- On that window, tap the Airplane mode.
- Now open the Phone app and tap Voicemail and then delete the voicemail messages.
- Turn off the Airplane mode. Your deleted voicemail messages won't come back.