Configuration settings for Yak commpartners

I have been able to configure Asterisk to accept incoming calls using using my WorldCity account but am having difficulty with outgoing calls. I am getting a “403 Forbidden” error message on the INVITE.

Is there any sample settings of sip.conf, particularly for outgoing calls using a WorldCity account? I can only find one link on an Asterisk site with some old settings.

Any lead is appreciated.