Apple Visual Voicemail requires an active data connection to work. If this is unavailable, you can still retrieve your voicemail messages by dialing the standard voicemail number.
Now, as for recording your actual voicemail, you will be prompted to say and record your full name as this is the default voicemail of the Samsung Galaxy S9. If you would like to customize it instead to be a personalized message, follow these instructions.

Visual Voicemail is supported by most modern iPhones. However, the carriers themselves also have to support Visual Voicemail. Most major carriers do, but you’ll want to check with your carrier specifically to see if the feature is supported.
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?