Closing out of your apps is like turning your iPhone off and back on — it gives your apps a fresh start. If one of the apps that you have open crashes in the background, it may prevent other apps you have open from functioning properly. It can be difficult to identify which specific app or apps are malfunctioning, so we'll close them all to save time. Double-press the Home button to view the apps your currently have open. Use your finger to swipe up on the apps to close them. You'll know all your apps are closed when you only see a preview of your lock screen.
Open the Phone app. Tap the Voicemail tab in the lower right-hand corner of the screen. If Visual Voicemail is not set up on your iPhone, you'll see a button that says, Set Up Now. Tap that button. Enter, then confirm a custom voicemail password. Tap Custom if you want to create your own custom greeting when someone reaches your voicemail box.

Once you click greeting, you can change it from default to custom and record your custom greeting. Press play to listen to it before saving it.
With this method, you don’t need a third-party app. Call the person you want to chat with, then tap the “Add Call” button on your phone’s screen. Dial your own phone number—the one you’re calling from. This will take you to your voicemail. Once your voicemail has started recording, tap the “Merge Calls” button on your screen. Now, you’ll record your phone conversation onto a voicemail message. When you’re done with the call, you can tap the share button to export it to your Mac via Airdrop, to the Voice Memos app, or transfer it via email or text message. The file is recorded as an M4A, so depending on what you want to do with it, you may need to convert it to MP3 before uploading it to other apps.