My wife's Centura has had a voicemail notification in the status bar for about a month even though she deleted all her voicemail. She's been out of state so after some searching I found a video on youtube about how to fix it. Although the video says the fix is only temperary and the voicemail reappears after a reboot, it's for a different phone. On my wife's Centura the icon is still gone after reboot so in this case it's a permanent fix. Here's the video:
Voicemail Notification Fix! - YouTube
Voicemail Notification Fix! - YouTube