There is a way in our system to make it mandatory for the buyer to enter in their phone number, but you will be collecting the phone number from all of your buyers, not just your non-U.S. buyers. To set this up follow these step:
1) Go to Seller Admin>Edit Payment Preferences;
2) Add a check mark to the box for the second option, Tell Payment Processor to Make it Mandatory for Buyers to Provide a Phone Number;
3) Click Submit.
The number that is collected will be included in the order data.