Hello, I'm a voip specialist with 10+ years of experience working on the level2/NOC department of a US voip company; I can install, troubleshoot and customize many sip devices including: softphones, ATAs, IP-phones and PBX systems like Asterisk/FPBX. I read your project description, and I can help you build your Asterisk solution on a good and cheap VPS, I'll also ensure your server is protected against common sip attacks, and also help you setup your extensions, trunks, x-lite or other free softphones, etc. You may contact me at any time to get this project started.
Thank you.