Action Voip in Ubuntu

1. Install ekiga with default option. This software is available in Ubuntu Software Center.
2. Open ekiga and do basic configuration. Basically decline registering ekiga account. 
3. Add action voip account using info as below:
      account name      : actiovoip
      registrar              : sip.actionvoip.com
      user                    : [which you get from registration page, you mentioned earlier]
      authetication user: [your actionvoip username]
      password            : [your actionvoip password]
      timeout               :600

4. Enable account. The account dialog should display the account as registered. If you dont see that. try enabling disabling account. If you cant succeed that part then we need some experts help.
5. Use SIP Domain sip.actionvoip.com. You can make call with this format sip:[destination phone number]@sip.actionvoip.com. Ex, you want to call +4902376421244, then you should type sip:+4902376421244@sip.actionvoip.com on your sip address 

Source:
http://ubuntuforums.org/showpost.php?p=8890657&postcount=7