We've been receiving calls from friends, family and clients in the US (using our old USA 541 area code phone number) for free over the past 11 months while living in Bali. (We are using a Google Voice number, since that' the number we had used as our main nphone number for years, but any number that can forward will do)
We've also been making outbound calls anywhere in the world for .01 per minute.
The thing that allows all this freedom is the little box pctured above (we got the OBI 100 model), that can be bought on Amazon and elsewhere for about $38 USD. It's about half the size of an iPhone, and connects to the ethernet cable coming out of your router. The other end connects to the phone of your choice. Once it's configured to a service provider (usually about a 5 minute process) you are ready to begin making and receiving calls.
We chose Anveo.com as our Session Initiation Protocol (SIP) provider because they were well reviewed and I liked their features, but, there are literally dozens of choices.
The OBi provides you with an abundance of control and enhanced convenience by combining a broadband Internet connection with VoIP . . . and if required, a land line connection to your local telephone company, your mobile telephone service provider or your broadband VoIP service. The OBi can use the web and social networking tools to bring everything and everybody together to speak freely . . . and even for free!