How do I set a country as a preferred phone number?
If you provide multiple countries in the list of long-distance (toll) or toll-free phone numbers for attendees, you can choose which country appears first in the list by designated it as a "preferred country".
If you do not have a preferred number, the first phone number that is displayed to attendees will be the billing country you have associated with your account.
Note: You can only have 1 preferred country.