1) Open the Skype for Business app.
2) In the top right-hand corner, tap the keypad icon.
3) Long press (press and hold) the 1 key.
NOTE: If you receive the error "Voicemail not available for this account", it may be because your Unified Communications account does not have permissions to use enterprise voice (EV), or you may not have enabled your EV service yet. For more information about voicemail service, please see How to: Determine if you have voicemail service with your Unified Communications account in Skype for Business on Android.
4) Follow the audio instructions to set up your voicemail or an out of office greeting. Tap the keypad icon to bring up the keypad as needed.
You have set a new standard voicemail greeting or an out of office voicemail greeting in TTU Unified Communications.
TIP: You may wish to configure voicemail and greetings options.