We know Skype has so far not jumped in on Windows phone 7 yet. To fill the game and allow cheap international calls easily without pulling out your calling card, Voxofon has released their cross-platform application for Windows phone 7 also.
The service provides international calls from 1c per minute and international text messages from 6c each, conveniently displaying the rate before the call is made. The service uses the normal cellular network to connect to Voxofonâ€™s VOIP gateway, so does not require a high-speed data connection.
Read more about the service at Voxofon here.