visual voice mail currently unavailable,what does that mean ?

Are you currently connected to the cellular network? If not, that would explain it. You have to be connected to the cellular network for VVM to work.

I went to my provider and everything is set correct just your voicemail visual not working

Who is your carrier and where are you located? Not all carriers support iPhone visual voicemail.

Buffalo my visual voice mail was working but I have too problems with this service