How do I cancel Out of Date Voicemail Notifications on a Nexus 5 Android 5.1?

[AC Question]

How do I cancel Out of Date Voicemail Notifications on a Nexus 5 Android 5.1,

I keep getting a Voice-mail notification that is 2 months old. Checking voice-mail - No message (Deleted when the message had been played at the time)

I am concerned if I clear Data from the phone App. it will delete all my contacts