List of country calling codes
This article is a travel topic
There are 9 calling zones:
Before dialling the area code, you usually have to dial an international prefix. This is so that the country code won't be confused with the first few digits of a local or national telephone number.
See the list at International dialling prefix.
Alternatively, if you have a mobile phone, you can dial the '+' key first before the country code regardless of which country you are calling from.