Create Offline Cellular calling framework

I require the freelancer to work on the development of a new mobile calling framework. This is how the framework should function, The owner of a mobile phone wants to make a phone call to his friend, he dials a predetermined number eg.9999999999 ( this is the number of the backend server owned by me ) , the call gets cancelled by the server immediately , and the server then calls back the owner of the mobile . When the owner picks up the call , he is asked to key in the mobile number of his friend whom he wants to call , The server then dials his friend and connects them . Basically, the server acts as an intermediately that makes a conversation call between 2 people . Note : THE ENTIRE CALL TAKES PLACE OVER CELLULAR NETWORK . THE OWNER OF THE MOBILE PHONE RECIEVES THE CALL FROM THE SERVER OVER THE CELLULAR NETWORK AND HAS THE ENTIRE CONVERSATION WITH HIS FRIEND ON THE CELLULAR NETWORK. BOTH PARTIES HAVE NO INTERNET CONNECTION NO APP IS NEEDED. I require a very intelligent and experienced freelancer who has industry experience and knows the technology. The framework has to be completed within 30 days .