To perform the Joy Fax Server correction, you MUST set up the area code and calls prefixes: 

On Server menu, click Server Options...; Or directly click Server Optionsbutton on the toolbar;
In the Server Options dialog box, type the Country or region code, your local area code, Long-distance and International calls prefix: 

Click Dialing & area code rules... button, to set up Dialing and Area Code Rules if it's necessary. For more information, please see this tutorial.
Click OK to close Server Options dialog box.

Note: First time you start the Joyfax server, the setup wizards will automaticly fill out above parameters. You also can correct Long-distance and International calls prefix manually, please see this page if you donn't know the prefix code:http://www.kropla.com/dialcode.htm