You will have a somewhat harder time working with the Virgin Mobile branded handsets in achieving free wifi calling. It might take a little bit of hacking on your part. Definitely consult @ howardforums.com in the VM sub-forum to see what options currently exist.
OTOH, you could quite easily configure an iPod touch to do this, and for free. Last night I finally got around to installing the Talkatone app on a 3rd Gen iPod Touch which enables free inbound/outbound VoIP calling. It uses my Google Voice account to be forwarded to the Talkatone VoIP app where I can send and receive (domestic)calls for free. There are some helpful instructions on getting the ball rolling at the Talkatone blog-
http://blog.talkatone.com/
I asked this in another thread, but it was related to the Optimus.
I dont yet have a cell phone. But I want to scrap my landline entirely and go cell. I talk a LOT on the phone at home, to family. I have been looking at the Virgin Mobile phones and plans. I want the cheapest way to talk unlimited at home (using wi-fi through my verizon dsl?) on the cell phone. And also to use it for checking email and such.
Can I purchase a cheap plan that would allow me some minutes while out and about, but is there a way to go through my dsl/wi-fi and get unlimitd talk and maybe surfing while at home?

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