Android phones can access voicemail by holding down the 1 key on the dial pad until the phone dials your 10-digit phone number. You will automatically connect to your mailbox and be prompted to enter your temporary password; this password is the last 4 digits of your phone number followed by the # key. Start the Google Voice app. Tap the three horizontal lines at the top left of the screen (sometimes called a hamburger menu), and then tap “Settings.” In the Voicemail section, tap “Voicemail greeting.” Tap “Record a greeting.” How do I access my voicemail? To call your voicemail on an Android phone, simply open your phone’s dial pad and hold your finger down on the “1” key. You can also call your voicemail from a different phone by calling your own number and tapping the pound key. How do you check your voicemail?
Visual Voicemail won't let me play back or adjust greeting. I have a new iPhone SE running iOS 9.3.1, restored from a backup of my old iPhone 4S. Also I have changed carriers upon getting the new phone to Cricket from AT&T. When I set up the new iPhone, it installed carrier updates from iTunes and the Phone app let me set up my visual voicemail

The service also recommends stating your name, apologizing for missing the call and that you will call them back. If possible include a time frame for a return call. Don’t ramble or include un-needed information.
3. Setting Up an AT&T Visual Voicemail: Open your iPhone's Phone app. It's the white phone icon on a green background on the Home screen. Tap "Voicemail". It's in the bottom right corner of the screen.