If you don't create call answering rules, incoming callers will be sent directly to your voice mail when you’re not available.
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.

In recent years, life has become so interconnected that we sometimes wish we could take some time off and not be obligated to check our phones every minute of the day.
Go to Account overview > My digital phone > Check or manage voicemail & features. On the Voicemail Settings tab, scroll to General Preferences and select Set Number Of Rings Before Voicemail. Choose a setting ranging from 1 ring (6 seconds) to 6 rings (36 seconds). Select Save.