When you make a call to an international number there's three parts you will need to dial. These are:
Exit code - Every country is assigned an exit code used when dialing outside of that particular country.
Country code - Every country is assigned a country code for incoming calls to that particular country.
Phone number - This is the phone number of the person recieving the call. (Make sure to include the area code, as shown below)
Example: 00 61 (Australia) 7 (area code) 12345678 (phone number)
Below is a list of International Country Calling Codes.