Hi,
before I submit my complete proposal I want to know following
1. Are using VPN tunnels between your offices
2. in other please confirm if you can provide a static public ip address
3. Do you want a single / center pbx in head office Or multiple system at each branch.
About me
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I am from Pakistan having 13 year experience with CTI (Computer Telephony Integration) and software development and have solid command on telecommunication related technologies, protocols and applications for example Asterisk, Freeswitch, OpenSIPs, FreePBX SIP, SMPP, IAX, WebRTC etc ... for details please visit my profile.
Regards