Unstructured Supplementary Service Data. Unstructured Supplementary Service Data (USSD), sometimes referred to as "Quick Codes" or "Feature codes", is a protocol used by GSM cellular telephones to communicate with the service provider's computers.

I need to make changes to my USSD application/Menu Unstructured Supplementary Service Data (USSD) is a simple, fast, powerful and efficient asset for a standard capability of GSM networks that transmits information over signaling channels. It allows mobile subscribers to use applications in near real-time, by typing few characters on their cell phone. USSD operations are typically initiated by typing a short code between hashes, for example *333*10#, which will return a result text directly and display a menu with more options. USSD works on almost every mobile phones platform and models, or to be precise, 99% of mobile phones worldwide supports USSD.