Truphone for Symbian

From Truphone:

Truphone is a new type of mobile operator that uses the Internet to give you free and low-cost calls and SMS on your mobile (via Wi-Fi or 3G). Because Truphone uses the Internet to carry your calls, there are no roaming charges or inbound call fees, so you can save money when calling or roaming overseas. Truphone works around the globe wherever you have access to Wi-Fi or 3G, so whether you're at home, at the office, or at your local cafe, you can make free and Internet-rate mobile calls. It's free to sign up and you get 2 or $2 free call credit when you join, so you can try it out without it costing you anything. This version is the first release on CNET Download.com.