Once done recording, go to the Voicemail greeting to find all the recorded voicemails. Click on the "Play" button beside the name of the voicemail to play it. To change the name of the recording, tap on it, and enter the name of someone who called you and set it as active. The caller will hear the voicemail greetings once they called you.
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.

For example, in the T-Mobile Visual Voicemail app, select “Settings” from the three-dot menu at the upper right of the screen.
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