i have an iphone 6 running iOS 11.0.3. I recently received a sound from my phone indicating a voicemail, even though no phone call preceded it. When I check my voicemail, I see a blank screen with 'Call Voicemail' in the center. If I push on the message a phone pad comes up for me to call voicemail. I've never done this so I called my own number. It asked for my password. I don't recall ever setting up a password. I made some guesses but they didn't work. Why am I getting this call voicemail message and is there anything to do if I can't recall my password?
You should probably call your carrier and ask them to sort it out.
Only your wireless carrier can access and manage the voicemail account for your phone number. On your carrier's customer-service page, look for steps about how to reset your password online or over the phone.