You can call and send SMS messages from abroad to all other countries.
For an overview of countries and prices, please visit https://undo.be/tariffs/roaming.
To call someone from abroad, you must add the + or 00 sign in front of the country prefix. Do not forget to remove the first 0 from the phone number. For example: you want to reach the Belgian number 0487030405 from abroad. You must dial the following number: +32487030405 or 0032487030405.