I've seen this issue a lot in people who are switching OS meaning going from Apple to Android or vs versa. You can not just switch your sim card over to another OS. Your service provider has to code your account correctly so it works. So if you have done this check your account is your device still showing as your old device. Call into your service provider and have them update your IMEI number and put the proper code on your account for you to receive voicemail.
I've worked at AT&T for over 10 years and yes there is a definitive difference in the coding side of service between devices.. This can also happen if you are going from an unlocked device to a provider locked device. For instance a pixel to a Samsung..
ALSO THIS IS NOT SAMSUNGS FAULT NOR IS IT YOUR PROVIDER OR YOURS. This is something that I would have to say 90% of people don't know and sometimes this issue doesn't happen right away it usually happens after an update to one of the multiple systems that are invalved in just the use of a cell phone.
The key issue with Visual Voicemail is making sure your voicemail is set up correctly first. Also if you have just switched phones from say an iPhone to a Samsung (like I did) then make sure that the carrier (AT&T in my case has the correct IMEI programmed on their systems). Sure you can swap the SIM card and most things will work but unless the carrier knows what device is connect not all things will work correctly. You will also experience a problem with iMessage and need to first disable iMessage on the iPhone before switching. Also make sure that Viisual Voicemail is enabled on your account.
For anyone who recently switched carriers and has an unlocked Samsung device. The native Visual Voicemail app was not working and it kept displaying error everytime it tried to refresh the inbox.
"Something went wrong.
We ran into a problem. Try again later.
If there's still a problem, contact Customer Service."
This is how I fixed my issue:
Settings > Apps > Find the voicemail app and select it > Storage >
1. Select "Clear cache"
2. Select "Clear data"
The app has been restored to manufacturer settings as if you just got the device out of the box. Close all applications and relaunch the voicemail app.
1. It will ask you for permissions to access calls, contacts, etc. tap "Continue"
Allow permissions for all the prompts.
2. It will then check your account information. Let it process while it fetches your account.
3. Now you will get the "Welcome to Visual Voicemail" screen. Tap "Continue"
4. Review and accept terms and conditions
5. You'll arrive at the voicemail inbox where it refreshes your inbox with your voicemails!
All is working now. I hope it helps everyone who has been living without Visual Voicemail!