This is based on a similar answered question for an unlocked S8 and it works.
THIS IS NOT FOR VISUAL VOICEMAIL. You can't get Visual Voicemail on an unlocked device.
To restore basic voicemail function with a notification do the following:
In something that sounds backwards, blocking the visual voicemail service on your line restores basic voicemail notifications on a smartphone the way we used to get them.
1) log into myverizon.com
2) go to 'my plans and services'
3) go to 'blocks'
4) Select your phone and click 'block services'
5) Turn on the blocking for VISUAL VOICE MAIL
* when you accept it will take you to a popup to verify changes and $$ changes to your account. there will be no $$ change unless you are dropping visual voice mail by doing this.
6) close out, wait a minute and reboot your phone
7) send a test voicemail. You will get a notification in the top bar that you have a message and the little recording icon in the notification bar. You have a message waiting!
dial your voicemail to get it. *86 from your phone dialer is the clunky way.
To streamline calling your voicemail...
1) create a new contact called VZ Voicemail or whatever you want.
2) make the phone number in the contact *86,xxxx# where xxxx is your voicemail password. the comma is a 2 second pause. This dials Verizon voicemail, pauses, then sends your password and #.
3) long press on the home screen... go to widgets
4) select the "contacts" widget group - select direct dial - long press to place it on homescreen
5) it will take you to your contacts - select the VZ Voicemail contact you previously made
6) you will now have an icon to dial voicemail with automatic password, you can move it to the bottom favorites tray if you want to.
unfortunately this is back to listening to the long version and having to press numbers to save, delete, etc. but at least it works.
7=delete, probably the most impt. listen to a whole message to refresh what the number controls are.
