Question : Using voip device to make call from mobile phone? Possible?

Assuming I have a Blackberry with a full data plan, how possible would it be to install a blackjack device (or any other voip device) in a PC, and somehow configure my blackberry so that I can use my data plan to make calls?

That way I would not need to purchase a separate voice plan to make calls. I can use my data plan to browse the web and make/receive phone calls.

To summarize, my question is: how can I use my mobile phone data plan to make and receive calls? Since I already have very fast full internet access, why not use it for calls too?

Any help is appreciated.

Thanks

Answer : Using voip device to make call from mobile phone? Possible?

Well, the first potential issue with solely using a device such as a Blackberry for Wifi/data calls (I know, you're talking about 3G/EVDO but it applies) is call quality (jitter/latency).  If you've ever used a wifi voip phone (netgear, cisco, etc) you'll know the situation has to be ideal for placing and making calls (3G/EVDO networks are generally worse).  Ideal can be a pain and my understanding is carriers don't have any COS/QOS on their data side.  So, let's assume we're past that and they do and it actually works and is usable...

I'm not aware of a provider that will allow you to drop a voice plan and just maintain data... so this might be a hiccup...

I had a few services in mind that I knew of and when browsing around for URL's for you I came across this:

http://voip.about.com/od/mobilevoip/a/BlackBerryVoIP.htm

It includes the sites I had in mind plus a few more.  I know people who have tried Skype (my favorite as I prefer more commercial apps) like myself and have found that mileage varies (i use it more of a novelty).  I don't know anyone that has tried it as their sole client, but heck, give it a shot.  I would like you to, even after you close this post, to come back and post results for quality, carrier issues dropping the voice plan, etc as I'm curious.  Some info like phone model (BB Bold, 8810, etc), carrier (ATT, Verizon, TMobile), and location (metro LA, podunk Alabama, etc), service you settled on (Skype, etc).  Thanks!