WhatsApp beta just received a new update with few interesting features. Now it has the option to send a voicemail when the voice call is not possible or if recipient declines the call.
These features were added in Android beta version 2.16.189.
After updating to this version, you will automatically get these options. If you call to a person on WhatsApp and other person does not pick a call or decline to receive the call, you will be shown a new kind of page. On this page, you have the option to either call back or record voice mail. You can see the screenshots above.
While you could send voice messages from Chat window, but this option lets you do it quickly from the after-call menu.
If you are interested in trying these features before it is officially available, you can download the beta version of the app. It is available on APK mirror. Download it here.