Key difference from SMS: USSD messages are not saved on your phone. The session ends when you close it.
Unstructured Supplementary Service Data (USSD), commonly known as or "feature codes," is a global communication protocol used by GSM mobile phones to interact with a service provider's computers. Unlike standard text messages (SMS), USSD creates a real-time session, allowing for instant, two-way interaction between a mobile device and a network application. What is a USSD Code? ussd codes