As you can see in the Frequently Asked Questions section from the official web page, you need to purchase an account in order to make a call from SJphone. With the free version of the program, you can only make a direct call to an IP address of your party, but be sure that there is no firewall that can block the application. Enter the IP address in the provided field and press the Dial button. You can go to Contacts > Help for further information.
