Why do my deleted voicemail messages reappear in my voicemail in box?
Why do voicemail messages that I have deleted reappear in my voicemail in box?
iPhone 5, iOS 7.0.6
Make sure you thoroughly complete all eight steps shown in the troubleshooting article you attached.
If steps one through seven don't solve it, then step 8 (contact your cellular carrier) is what you should do.