5. Switch on and switch off Airplane Mode. You can do this from either Settings or the Control Center. On iPhone X or later, swipe down from the top right of the screen (where the battery indicator is).
To transfer your existing voicemail, follow these steps: Go to the Phone app, then tap the Voicemail tab. Tap Set Up Now. Enter your password,* then tap done. Record a custom greeting or use the default greeting, then tap Save. * If you forget your voicemail password, there's no …

The simplest, lowest-tech option—beyond operating a recorder while you blather over the speakerphone—is a cable: the Olympus TP-8 Telephone Pick-up Microphone for under $20. It doesn't digitally capture from your iPhone. Instead, it has a microphone built into the earpiece. Plug the 3.5mm plug on the other end into a recorder. Hold the iPhone up to your ear to talk normally. The TP-8 captures each side of the conversation from what comes out of the iPhone's ear speaker, while you can still hear the conversation.
You will be asked to delete your current Voicemail greeting. Click on the ‘Yes’ button that appears on the screen if you want to remove that. You can save your new recorded Voicemail greeting or can use the default recorded option. Wait and hear the new Voicemail greeting message that the instructions speak out. If you want to keep that recording as your Voicemail greeting, then save it. Or you can re-record the message to get a different greeting.