While most of GTalk2VoIP services are available free of charge, some of them require payments (credits on your balance).
To buy credits you have to:
1. Open your Talkonaut or Google Talk and type MYPAGE to firstname.lastname@example.org.
2. Follow the link you are displayed. This will lead to your personal account page.
3. Click on "buy credits" link in the top of the page.
4. Choose the way you would like to pay (we accept credit cards with "Authorize.Net" or "Paypal") then click a desired amount button.