Download the Gizmo(http://www.gizmoproject.com/) client and create an account. In Ekiga(http://www.ekiga.org/) select GSM as the preferred audio codec, using the preferences dialog. Buy some credit in Gizmo website.
Instructions to configure Ekiga:
In Ekiga select GSM as the preferred audio codec.
Add an account
Account Name: Gizmo
Registar: proxy01.sipphone.com:5060
User: GIZMOACCOUNT
Password: GIZMOPASSWORD
Authentication Login: GIZMOACCOUNT
Realm/Domain: proxy01.sipphone.com
How to dial a normal phone:
For phone number + 1 543 234 3456 use sip:0015432343456@proxy01.sipphone.com
