To activate the feature from most UT phones: Hang up the receiver, pick receiver back up and press *57 (star-five-seven) immediately following a threatening or harassing phone call, and before making another call.
Essentially, *57 records the calling number and other identifying information such as the date and time of the call. This information can then be used to request a complaint with your phone provider or to report the call to law enforcement.
*57 (or 1157) must be dialed immediately after the harassing call. and prior to receiving another call or hearing the call waiting tone. You aren't charged for unsuccessful attempts. You are billed for all successful traces, even if there is no follow-up action.
You don't need to talk to the caller—just quickly pick up and then hang up again. Hang up and dial *57. As soon as you hang up the call, pick up again immediately and dial *57. For most phone providers that offer this service, you'll need to dial 1157 instead if you have a rotary phone.
Call return (*69) automatically dials your last incoming call, whether the call was answered, unanswered or busy. Call within 30 minutes, during which you can still make and receive calls. To deactivate while waiting for the party you are trying to reach to become available, dial *89.
Caller ID Suppression
To activate, dial *65, then the number you wish to call. Your caller ID will be blocked on the current call only.
Auto Redial is a service that dials a number that is busy for up to 30 minutes and alerts you with a distinctive ring when the line is no longer busy. To activate Auto Redial, press *66 (1166 from a rotary phone). To deactivate Auto Redial, press *86 (1186 from a rotary phone).
This Vertical Service Code, *82, enables calling line identification regardless of subscriber preference, dialed to unblock withheld numbers (private callers) in the U.S. on a per-call basis.
Call Block, otherwise known as Call Screening, is a feature that allows you to block calls from up to 10 phone numbers within your local calling area for a low monthly rate. Turn on: Press *60.
You can use this feature to trace unlawful or threatening calls that alarm, frighten, or harass you. Your phone is already equipped for Call Trace, simply press *57 to activate; there is no charge for the connection.
Reject anonymous calls
Anonymous Call Rejection (*77) stops calls from people that use a blocking feature to keep their name or number from being displayed. When Anonymous Call Rejection is turned on, callers will hear a message telling them to hang up, turn off the blocking feature, and call again.
Hide Caller ID: *31#
You might have received a call from unknown number. The caller might have hidden the ID intentionally or sometimes it can be accidental. If you want to hide the caller ID dial *31# and press call button.
Use *67 to hide your phone number
This trick works for smartphones and landlines. Open your phone's keypad and dial * - 6 - 7, followed by the number you're trying to call. The free process hides your number, which will show up on the other end as “Private” or “Blocked” when reading on caller ID.
Private numbers, blocked, and restricted calls can usually be traced. However, unknown, unavailable or out of area calls are not traceable because they don't contain the data needed for a successful trace.
Immediately after a missed call from an unknown number or a number that shows up as No Caller ID, dial *69. From here, you will be able to trace the number—and name and address if listed in a public database—to reveal the number and possibly more information about the identity of the strange number that's calling you.
Code: *#30#
If the recipient of your calls isn't able to view your mobile number, there might be a problem with your number's Calling Line Presentation. In that case, you can use this code to check if Call Line Presentation is enabled or disabled.
To bar all incoming calls and texts:
Dial *35*<4-digit code># on your mobile phone and press the call key.
The next time you receive a call from a number you wish to block, end the call and dial *97. The number will automatically be added to your Selective Call Rejection list. You can block up to 100 numbers.
General Test Mode: *#0*# Display your IMEI: *#06# Check Your Call Forwarding: *#67# Get Even More Info on Call Forwarding: *#61# Check Your Available Minutes: *646#
Key hardware info: *#0*#
When you enter *#0*# into the phone's dialer, the device enters service mode and brings up a diagnostics menu. From this screen, you can view and run multiple diagnostics to test device hardware like buttons, sensors, and cameras.
Call barring lets you block incoming or outgoing calls to and from your phone. This may be useful if you keep receiving unwanted telemarketer calls or want to avoid expensive international calls. To check if the feature is enabled on your device, dial *#33#. Use the code *33*pin# to enable call barring on your iPhone.
When you dial *#21#, you are, in fact, activating a feature access code that quickly tells you the status of call forwarding for your phone. It's a quick way of seeing what, in the case of this particular 'setting interrogation code,' your call forwarding settings. That's it, nothing more or less.
Block calls from your phone
Press *80 to turn call blocking off.
*#21# - By dialling this USSD code, you would get to know if your calls have been diverted somewhere else or not. *#62# - With this, you can know if any of your calls - voice, data, fax, SMS etc, has been forwarded or diverted without your knowledge.