dialling 123 from your phone and following the instructions.dialling 07782 333 123 from any other phone and following the instructions.dialling +44 7782 333 123 when you’re abroad and following the instructions.
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?

If you've forgotten your retrieval number, call 800-244-1111 to get it. Alternately, the number was included in the welcome letter you received when you signed up for voicemail service.
Changing default voicemail to the custom greeting is very simple until iPhone won’t save custom voicemail greeting or custom voicemail greeting on iPhone not working issue arises. Don’t worry, you are not the only one with this problem, till now many users have fixed the unable to change voicemail greeting on iPhone with the help of below solutions.