Hi,
I have been working with Cisco VoIP since 2001 and Asterisk and freepbx ,trixbox, elastix since 2007.
In addition to installing Freepbx and setting up the Queue and Agents,
I would also recommend and setup OFF-Time greetings and Voice mail for it,
Also for Security, I would recommend to change the defaults ports not only for SIP (5060) but for
AMI (5038), RTP (10000-20000), Http (80), Https(443), SSH (22) etc.
That being said I would like to have a little chat about your project to better understand the needs of the project
regards,