Telephoning Kia from International may not be possible because of their short number - it may be a special number like a US 1-800 that doesn't work internationally.
Australian landline telephone numbers are 8 digit.
Australia uses eight digit local phone numbers preceded by a two digit STD area code.
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So the quoted 6 digit phone number is something odd.
The Australian country code is 61. When calling from outside Australia, leave out the leading '0' from the STD area code or from the mobile telephone number.
Example: Fixed line example calling Canberra from outside Australia: +61 2 (local eight digit number)
The Area Code for NSW is probably 02 but some areas may use the 08 and 03 area codes instead.
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Alternatives, why not use a simple local telephone? Payphones still exist, or your accommodation should have some kind of telephone. You could also purchase a "prepay" or "pay as you go" sim and see if it works in your phone. Or purchase a cheap cellphone for the time you're in Australia, and gift it to someone else before you leave.