Dial the international prefix 00 first, then the country code+city code+the recipient's phone number.
For example, dial 12345678 in midway, USA. That's 00+ 1 (American country code) +808 (midway city area code)+12345678 (customer number).
Another example: the number of a mobile phone in Thailand is (0)9 1044029. You should dial: 00 (China dial number) -66 (Thailand dial number) -9 1044029 (called number).
So add 003 1 before the phone number, and then the called number. If the first number is 0, omit the above example.