need pbx/VoIP/SIP help

Im looking for a coder to make me a simple web app that can make calls using open source software like Asterix or another one of the SIP/PBX code. I'd like to create/add a phone number and have this system re-direct it somewhere else and keep track of call volume etc. I'd like some help understanding what's required for this, costs, hardware, software etc. I know asterix can handle a lot of this, but its not clear to me what actually connects a user to a phone line, if a third part needs to be involved or what. Thanks ## Deliverables 1) All deliverables will be considered "work made for hire" under U.S. Copyright law. Employer will receive exclusive and complete copyrights to all work purchased. (No GPL, GNU, 3rd party components, etc. unless all copyright ramifications are explained AND AGREED TO by the employer on the site per the worker's Worker Legal Agreement). 2) Complete and fully-functional working program(s) in executable form as well as complete source code of all work done. 3) Deliverables must be in ready-to-run condition, as follows (depending on the nature of the deliverables): a) For web sites or other server-side deliverables intended to only ever exist in one place in the Employer's environment--Deliverables must be installed by the Worker in ready-to-run condition in the Employer's environment. b) For all others including desktop software or software the employer intends to distribute: A software installation package that will install the software in ready-to-run condition on the platform(s) specified in this project. ## Platform flexible, all needs to be cloud hosted (virtual private server)