When receiving a call, it never matters for you where the call is coming from. It is the same for all carriers when it comes to that. To make any overseas calls, you must purcahse a separate long distance add-on. If you don't have that add-on, you will not be able to make any outgoing overseas calls. The only option that Public Mobile offers for this is 400 minutes for $15 (calls rounded up to next full minute/per minute basis). Keep in the mind that only works for certain countries. Countries other than the 18 included country list cannot be called at all.
There are always paid/per minute long distance options available through many different companies. These involve calling a local access phone number first and then it asks you to type in the number you want to call. These services are separate from Public Mobile other than Public routing the call to the long distance company's local number.
Apps such as Skype, Viber, Facebook, Hangouts, etc. can make calls to people who are overseas, but to be able to make these calls for free, the other person you are talking to also needs to be using the same app/software program. Some of these apps have options to make calls to people who are not using the same app, but those calls usually cost extra with the need to provide a payment to the company running the software platform.
