This paper describes an interactive social agent platform which examines anthropomorphic robot features in the mobile phone usage context. Our system is smart phone based robot agent that operates on a mobile network and co-located ad-hoc networks. It helps remote users communicate interactively with each other through the robotic interface which utilizes facial expressions and body gestures. In this paper, we introduce the mobile environment as a service platform for social robots, and discuss design considerations for such a communication system. Then we illustrate the development of our system followed by its network protocols built on existing mobile services such as Telephony and Short Messaging Service (SMS). Usage scenarios and working prototypes of the implemented system are also presented. We are hopeful that our research will open a new discussion on socially interactive robot platforms, and thus, that such efforts will enrich the telecommunication and personal robot services in the near future.