International Calling Through Wifi

[jr8810]

Hi everyone!

I'm visiting Europe in a couple weeks and purchased an unlocked Blackberry Curve 8320 (originally from T Mobile) so that I can pop in an international SIM card and make calls while there.

However, I am going to have access to wifi while there and was wondering if it's possible to make calls back to the U.S. through wifi through some mobile app or website. I'm sure there will be international rates, but I doubt they'll be as high as the ones other companies charge.

P.S. Since this phone is not active with any service provider right now, I can only access websites through wifi...cannot use 3G.

Thanks in advance!