Voicemail disappeared and Now can't set up again

Had voicemail for years (iPhone 5/10.3.4). Then disappeared, and callers heard, Voicemail not set up.

When I went to set up, I get message that can't be set up and try again later. But screen then says, "Setting up voicemail...." only way to move from that screen is to restart phone. Then try again, record answering message, and again get message that can't set up, try later, and Setting up voicemail screen.

Thanks for help