I am really not loving this Samsung support model, which appears to be "let's start a community and let users solve each other's problems and we won't have to do anything at all" and maybe you can hope that Samsung support will see your post and weigh in.
Samsung must develop a way to dismiss persistent notifications. I don't need a constant notification on my watch of a voicemail that does not exist. It wastes battery power and annoys the user. THERE IS NO VOICEMAIL. At the very, very least, the notification should disappear when the voice mailbox is accessed (message or not). There also is absolutely no reason for a notification to be ongoing. If a user saw a notification and chose to ignore it, there is no reason to keep reminding them of it. ONGOING NOTIFICATIONS SHOULD NOT EXIST.
I noticed that even when there is a legitimate voicemail notification, I cannot dismiss it until I access the voicemail. This is wrong. At the very least there should be a setting whereby you can a) select if you want notifications to be ongoing and b) select how many times and at what intervals you want to be reminded, or c) not have an ongoing notification at all.
I understand this particular issue seems to be with the Galaxy Watch 4 and T-Mobile, and T-Mobile says their Samsung tech liaison team is working with Samsung, and Samsung will, supposedly, eventually come up with a fix for it. But it would not be happening in the first place if any of the suggestions above were utilized. I also understand that some people have had success with resolving this issue by factory resetting their watch. I refuse factory reset my watch for a minor issue, especially when the backup data may contain whatever error is causing this, and I don't want to have to go through all my settings again after a reset, just to get my watch to function properly.
I personally don't use the LTE version so I cant really share the same experience, I would suggest you report the issue using wear app > menu > contact us > error report after reproducing the issue.
I saw a post on a similar thread yesterday. The solution has been found:
Reset your mobile plan, then factory reset watch.
I HIGHLY recommend you be on the phone with your carrier at the time. Mine is T-Mobile, and they had to reattach my watch to my account.
Hey Samsung.... why don't you spend some time fixing this voicemail issue. It has gotten old very fast. Last time I sent my Gear 3 Classic in to repair you lost it. So I'm a bit untrusted of sending to repair when it's a software issue. Payed good money for this dang wat h and I'd like it to work right.
I have tried everything to remove the voicemail notification from my watch. This is a brand new watch, not even a week old. It started today. It keeps notifying me that I have a voicemail. Meanwhile I have checked over and over and I have no messages. I turned both the watch and phone on and off several times. Took the Bluetooth off. Tried calling the number to which the watch is connected to leave a message to see if I can then delete it. Nothing. I am at the point of returning the phone. All it does is annoy me and uses up the charge on the watch.