Carriers also don't want regular customers using these codes and often deactivate or change them as needed. If you want to try them out, first do a web search of your phone's make and carrier + "USSD" ...

Some examples of what you can do with USSD codes are checking the IMEI, changing call forwarding settings, seeing advanced network details, and more.

Type USSD codes on your iPhone to access hidden cellular features quickly. Here, we'll list some of the most useful ones.