Voicemail password

I get messages through Visual Voicemail and it works well for the most part. 

One problem, and it may not be an issue with VV, but I have noticed on two different Samsung phones, an S10 and an A53, that I can delete a message from VV, but the notification that tells me I have voicemail still appears. I can call voicemail from the notification, but before I can access the message I have to log in with a password which I guess must be a series of numbers. I don't remember setting up voicemail outside of the VV client. How can I either reset my voicemail password or disable the notification. I do not want to disable notifications from VV.