I put in *#21# in my smartphone's dialer, and it says everything is forwarded?! Should I be alarmed?
Short answer: No. Long answer: GSM phones let you put in these dialer codes to change some settings. The codes, collectively, are known as USSD (unstructured supplementary service data) codes, sometimes called "quick codes". These settings are NOT in your phone, but on your mobile carrier's computer as a part of your account. Generally speaking, USSD codes are used to add or remove service, or change some settings for the service. Some carriers use it for payment notification and payment status. Actual active codes are dependent on the carrier. As this is often used to just show the status of something it's also called interrogation codes, or feature access codes. So what does *#21# actually do (note: it's actually asterisk - hash - two - one - hash)? It shows the status of call forwarding set to the five types of calls you get: voice, SMS, fax, data, and system. (NOTE: some phone vendors only show voice, SMS and data, not fax or system) And in all cases, it ...