international calls with at&t prepaid

No, international calls are not included and ATT does not offer free international calling for prepaid. You can add an international calling plan that reduces cost. I do not know the rate to call Australia but plan on $3/minute without an international plan. 

Moving to PRE-PAID.

Hey there, we're here to clear up your options for calling Australia internationally when you have AT&T PREPAID service, @KamP.

Our PREPAID plans don't include a free option for calling Australia when you're out of the country, like our ACE @sandblaster mentioned. In order to make these calls at a discounted rate, you'll need either our PREPAID International or International Plus add-ons, which are $10 and $15 per month respectively. 

With the $10 per month International add-on, you'll get 250 minutes of calling from the U.S. to 70 countries, including Australia, at no additional cost. If you have the $15 per month Internation Plus option, then you'll get unlimited calling to 85 countries, including Australia, and discounted rates for 140 other countries.

Without either of these above add-ons, calls to Australia will be $4 per minutes, as mentioned on our PREPAID International calling rates and add-ons comparison page, where you can see which countries have a discounted rate with these add-ons or not. 

Please let us know if you have any other questions about this, or anything else.

Dylan, AT&T Community Specialist