Visual Voicemail won't Activate due to "Associated with another account"

I have a new zflip, and I set up my visual voicemail with no problem when I got it a few months ago.  But just this last week or so, I have been having the same problem that the original starter of this post had.  I have tried just about all the same things mentioned above.  I spent time on the phone with the mobile tech, and it seemed to work for a minute. Then later when I tried to go into it, it did exactly the same thing saying it appears to be associated to a different account.  And I keep setting up a new account because, if you don't, it won't let you do anything else but logs you out.  Is there another way to use voicemail without having this specific app?  This is really getting annoying!