My IPhone XR is stating I have a voicemail that is not set up
A few weeks ago people told me they could not leave me a voicemail anymore because my voicemail was not set up. I have tried everything shown online to reset my phone so that my voicemail will work. It is set up. It is on. I have double checked all the settings, reset the network. BUT, it still says I have a voicemail that is not set up! How can it be set up, I can hear my voicemail greeting, but it says it is not set up!!