Hello!
Is only pay per use charges, (according to your balance) if you have a 20$ plan/month it will cost you more per minute but if you have a 25$ plan or more per month is cheaper with the "international talk saver" rate.
For example, if you want to call Australia # it will cost you 50 cents/min for both land line or cell# with a 20$ plan/month... and is 3 cents/min to a land line or 15 cents/min to a cell# with 25$/month or more per month.
In order to call for international, you need to add extra money in your balance first.