I am Linux Admin and Ethical hacker and cyber security engineer. Setting up and managing the connection for a call Tearing down the connection when the call is complete Billing Managing call forwarding, calling party name and number display, three-way calling, and other Intelligent Network (IN) services Toll-free (800 and 888) and toll (900) calls Wireless as well as wireline call service including mobile telephone subscriber authentication, personal communication service (PCS), and roaming