Smartphones have evolved a long way since the advent of feature phones into this world and such an evolution has transformed the way we could unlock hidden settings of a phone or an iPhone in a jiffy. The hidden iPhone settings could often hold the key to simple status displays to something more complex like improving the phone's voice quality or as eerie as hiding your number on the recipient's handset.
Note: IBTimes SG reminds its readers that the information provided in this article is for reference only. The publication will not be held liable for any damage caused to the device during or after using these USSD codes, and hence users are advised to proceed at their own risk.
Regardless of your diversified needs and intentions, here are a bunch of USSD codes that can be entered into your handset using a handful of digits, characters and a simple tap on the call button:
*3001#12345#* – It will put your handset into Activate Field Mode which contains all of your iPhone's technical settings. It can also convert the signal bars into an actual number.
*#5005*7672# – This code will help you check SMS center
*646# (Postpaid only) – It displays your available minutes
*225# (Postpaid only) – It checks your current bill's balance
*#31# – It helps you choose if you want to hide your number
*3370# – Enable or disable EFR (Enhanced Full Rate) which improves your iPhone's voice quality, but will quite likely reduce battery life
*#21# – It enables you to check call-forwarding status
*777# (Prepaid only) – It checks the account balance and retrieves the status in a message
*#62# – It allows you to verify to which number the calls will be forwarded to, if no service is available
*#76# – It checks connecting line presentation
*#67# – You can check the number to be used for call forwarding
*#33# – You can check whether anything is barred, such as international calling etc.
*#61# – Check number of missed calls
*#06# – Displays your iPhone's IMEI number
*#43# – Check the call waiting status
*43# – Activate waiting
#43# – Deactivate call waiting
[Source: Redmond Pie]