Can't retrieve voicemails after iPhone 6s reset

A couple of days ago I had my iPhone 6s reset through your device; after all is good and done I see my voicemail can’t be retrieved to listen to my voicemail messages. When I try there is a hour glass that has appeared and it the had a message to hit ‘go’ I then hit it but it all disappeared and I still can’t retrieve my messages. What do I do to reset my voicemail?

[Re-Titled by Moderator]