Hello I'm a voip specialist with over 10 years of experience working on the TS department of a US voip company; I can install, troubleshoot and customize many VOIP devices including: softphones, ATAs, Ip-phones and PBX systems like Asterisk/FPBX. I read your project description and I can help you build your A2billing dial-plan/routes. You may contact me at any time to discuss this project further.
Thank you.