Abstract: The invention is a system that provides and manages a graphical user interface on a mobile device to allow the mobile device to interact with a remote service portal using a Short Message System (SMS) interface. The system includes: a client application running on the mobile device; a Graphics over SMS (GoSMS) protocol comprising a language for exchanging commands, responses and data between software applications; a GoSMS message manager running on the mobile device; and a GoSMS server running a conversation management engine. The conversation management engine is a software application that exchanges SMS packets with the GoSMS message manager. The GoSMS message manager mediates the transmission of messages between the client and the portal by encoding GoSMS messages from the client in a number of SMS packets, and assembling multiple SMS packets received from the portal into GoSMS responses.