After you hang up, the recorded call will appear in the Voicemail section of your iPhone’s Phone app. The Easiest, Most Versatile Method: Just Use Speakerphone and a Recorder. At the end of the day, the best and most simple method for recording calls on the iPhone is doing it the old-fashioned way: Speakerphone and a recorder of some kind.
On the iPhone, go into voicemail and tap "Greeting". Record a few seconds of something and tap stop. Before you tap save, use iFuntastic or SFTP to navigate to /var/root/Library/Voicemail on your iPhone. You'll see a file called "Greeting. amr". This is the audio you just recorded. Delete that file and replace it with your custom message which should then be renamed to "Greeting.amr". Tap "Play" on the iPhone to verify your message works. If it plays, tap "Save" and your custom message will be uploaded to AT&T's servers.

Recording Phone Calls on an iPhone Without Using Apps This method can be considered as the easiest, fastest, and perhaps “dirtiest” way of recording a phone call from an iPhone. All you basically need to make this work is another device that has a microphone that can record (like a computer, iPad, or a portable recording device).
This might happen when you enter your messagesafter you restored iPhone, updated to the newest iOS, reset all settings, etc. Most probably, it’s caused by some cache files deep in the system. When your iPhone is repeatedly asking for Voicemail password, don’t panic. Totally, there’re 3 ways to reset voicemail password on iPhone as listed below. 3 Ways to Reset Voicemail Password on iPhone 11/X/8/7/6s/6/5/SE 1. Reset Voicemail Password through iPhone 2. Use Automated System to Reset Password (Call 611) 3. Reset voicemail password from your carrier’s website (AT&T, Version and Sprint) 1. Reset Voicemail Password through iPhone