Problems with my voicemail (Iphone 6s plus)

When I click on my phone icon, the voicemail icon has a blank red dot on it. Clicking on voicemail, the screen reads 'call voicemail'. From the reading I've done I understand this to be a visual voicemail problem, however when I go into settings and try to reset my voicemail password I receive a message that says 'voicemail unavailable'. I have set my voicemail up, I have received voicemails which I can access by calling my voicemail. I have tried turning on and off airplane mode, resetting the network settings, powering the phone on and off, and having others call me. Nothing has removed the red dot nor allowed me to reset the password and I still don't have a voicemail log visible. Any suggestions?