When you first set up your Android phone, it may ask you to record your greeting for the caller. You can also keep the default greeting stored on the device. But, in future, if you want to customize the Voicemail greeting or want to create a new one, then you may need to delete the old recordings from Android. It may not be necessary depending on the Android device model & version; it’s good to know the process.
Press and hold 1 on the dial pad. Next press the * key, then press 3 to be brought to the Greeting page. Finally, press 2 to record your own personal voicemail message. Simply press the # key when you are done recording.

When starting a Voice Recording you can choose between 3 different recording modes, you can select either Standard, Interview or Speech-to-text. When using Interview mode the sound is amplified from the top and bottoms of the device and reduces the sound from the sides. This mode works effectively when recording sounds in a noisy surrounding.
28. Hello, you’ve reached [your name]. I can’t come to the phone right now, probably because I’ve just stepped away from my desk, but possibly because I’m trapped under something heavy. Leave a message and I’ll call you back within one business day — and if I don’t, please send help.