Iphone 11 or Verizon is blocking a callback from a doctor on my health app

My workplace requires us to use Teladoc before going to the doctor. I have used this successfully in the past by signing in through the Teladoc app and requesting a callback from a doctor. For the past week they've been trying to call and NOTHING is showing up on my phone - no phone call notification, no voicemails. When I go back in to the app it says they've attempted to call back three times and I "may need to disable anonymous call blocker to allow the doctor to reach you. To deactivate anonymous call blocker, dial *87 on your phone. " Can anyone help with this!!???