Hi,
I have been working with Cisco VoIP since 2001 and Asterisk and freepbx ,trixbox, elastix since 2007.
I can get you an interface to get call details and costs for any particular extension based on the check-in and check-out dates,
I hope that is what you are looking for ,
Kindly let me know if we can have some chat about the project to better understand the project.
regards,