Why are my messages using different Voicemail #'s than the ones set in call settings?

[AC Question]

Messages is using different Voicemail # than set in call settings

I have set the voicemail number in the dialer app with my VM number, but when i respond to a VM alret in the default Message app, this VM alert auto-dials a short 5 digit code that I don't recognize and cant find in settings. I have a new Samsung Note 5 with Android 5.1.1. I've checked the forum and don't see an answer to this issue. Many thanks to anyone who can figure this out.