In the Settings, one would be "Phone book'
You can become listed in the "Phone book" with and on/off toggle
You can set and change your "Phone book" name at any time.

When you're ON, anyone can find you and call you from any other Portal, if they use the search name you specified.

This allows people that may NOT be on your Messenger list, but IS another Portal user to call, without being added as a friend in Messenger.

Also, a twist on this that would open Portal up to more business use and group use.

In the same panel where you can enable this "Phone book" listing you can also add an identifier that would add you to a Group Call list.

If your Doctor, Group or organization placed a call to the specific group call identifier that represented the group of people that added this identifier on this page in the Portals' set up, everyone on the list would get a call.

You can allow multiple group call identifiers

This would open Portal up to more casual calling.