Context does matter here. If the caller would reasonably expect you to answer the phone (such as if they were calling a store or other place of business), an apology for not being able to get to the phone makes the most sense.
On your Android device, open the Google Voice app .At the top left, tap Menu Settings.In the Voicemail section, tap Voicemail greeting.Next to the greeting that you would like to use, tap more Set as active. To change your voicemail greeting: Go to Phone > Voicemail and tap Greeting. Then follow the prompts to change the greeting. To change your voicemail password: Go to Settings > Phone > Change Voicemail Password and then enter the new password you want to use.

This works for any call, live conversation, or endless Zoom call. On a second device—be it another iPhone, an iPad, laptop, or Android phone—open a voice-recorder app and hit record while you're talking. On iOS, the built-in version is called Voice Memos; we have a full tutorial on how to use it. Windows 10 has a built-in Voice Recorder. Android has a bunch of them.
The default voicemail greeting on the iPhone plays generic Your call has been forward to an automated voice message system recording. If you use your phone for work, create a personalized greeting that tells people you're a professional. If your phone is for personal use, create a personalized greeting so people hear your voice and know they called the right number.