To call your friends worldwide it's easy, you just need to use the international format:
+ (country code) (area code) (number)
Here are some examples :
To call your friend in France, dial : +33 ( erase 0 from area code) (number)
To call your friend in Mexico, dial : +52 (area code) (number) or +52 1 (area code) (number) if you want to reach a cell phone with a 2 digits area code,
To call your friend in Philippines, dial : +63 (area code) (number)
To call your friend in Pakistan, dial : +92 (area code) (number)
To call your friend in Chili, dial : +56 (area code) (number)
To call your friend in UK, dial : +44 (area code) (number)
...
Don't forget the "+" , do not dial 00
(tap a long 0 to dial +)