How can i make free PC to PHONE calls ?

How can i make free PC to PHONE calls ?
Is there a particular software needed to perform this task?

PLZ HELP!

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How can I make FREE voip calls from Jamaica to USA?

Earthcaller use to work PERFECTLY. . . i mean the thing was just heaven sent. But now it must be under construction or something because it is denying access. Is there anything else that I can use to call USA from Jamaica. Free PC to PHONE calls, not PC to PC.

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