Your project is under estimated for its price. The requirements are Huge, we have done similar earlier, will send in documents in private message once you will respond.
We are VOIP professionals Experts in freeswitch and similar VOIP applications, With US you have the advantage of being with an organization above freelancers.
We build, Customize and Support the end to end solution for you.
We have several happy VOIP clients out there. We suggest you to choose professionals over freelancers.