I've set up my voicemail on my new iphone4s but whenever anyone tries to leave a voicemail they get an annoying siren like sound. I also get that sound if I *86. I took the phone to a verizon store and they said it's not on verizons end its an iphone problem. I find this a little hard to believe -- I've had the phone for about a month now and voicemail is still not working. Does anyone have any suggestions?