One day I was just flipping my phone open and close and pressed some unknown buttons accidently. When I tried to call my voicemail later on I got a busy signal. I looked online for some solutions but none of them worked so far. I've had this problem since October and everyone else in my family has their voicemail working. The message a person gets when they go to voicemail is something to the effect of, "Welcome to Verizon Wireless. The customer you called is not here at the moment, please call again later." Then the voice says "Announcement 1 switch 122-12" If it matters I have a Samsung Alias 2.
You may have accidentally enabled the Call Forwarding feature. Try dialing *73 and then Send from your phone. You may hear a couple brief tones and then the call disconnects. Then try calling voice mail *86 send. If that works, then have someone call your phone and don't answer to be sure it's routed to voice mail correctly.
If that doesn't work, you will need to contact customer care from another phone than yours but have yours handy for troubleshooting. 800-922-0204 or *611 from another VZW mobile.