When adding a contact to your V.ALRT make sure you use international dialing format that starts with a plus sign (+), this can be done by holding down the "0", then write the country code, followed by the full phone number. Make sure to remove any leading 0′s or any special calling codes.
For example the United States number 123-4567 and area code 954 would be written as +19541234567 (1 is the country code).
Remember that some countries add some digits after the country code for mobile numbers. i.e. in Argentina, mobile numbers should have a 9 between the country code (+54) and area code. The final phone number will have 13 digits total: +54 9 xxx xxx xxxx. In Mexico, mobile numbers need to have a 1 after +52, even if they are Nextel numbers.