Yes, someone can lock your SIM card by repeatedly entering the wrong PIN, requiring a PUK code from your carrier, but you can prevent unauthorized use by setting your own SIM PIN in your phone's security settings, which blocks calls/data until the PIN is entered, protecting against SIM swaps and unauthorized access to your number, especially for 2FA codes.
Locked Sim refers to it having a passcode usually referred to a PUK code. It means the sim cannot be used and as such you would have no service at all. A Locked sim card cannot be used until the Sim Pin or PUK code is provided.
One of the first signs that your SIM card is cloned is when you suddenly stop receiving calls and messages or cannot send them. Loss of connectivity can signify that an attacker has initiated a SIM swap, transferring your phone number to their new SIM card and blocking yours.
For Android devices
Go to 'Settings' on your Android device. Look for 'Network & Internet', 'Connections', or a similar option, depending on your device. Select 'Network Operators' or 'Mobile Networks'. If your device allows searching for and selecting different network operators, it's likely not SIM-locked.
The reason many network providers SIM lock their phones is that they offer phones at a discount to customers in exchange for a contract to pay for the use of the network for a specified time period, usually between one and three years.
You can try to make a call to the phone number of the SIM card to see if the service provider will prompt you with a voice message. The other option is to send a USSD command to the service provider and note the response.
Common causes of a blocked SIM card
A SIM card can become blocked for several reasons: ❌ Incorrect PIN entered too many times → requires the PUK code to unlock. ❌ Network lock on the device → the phone only works with a specific carrier. ❌ Compatibility issues → different network bands, technologies, or regions.
Dial codes like *#21# or *#62# help check call forwarding settings, but they can't confirm if your phone is hacked. They're useful for spotting suspicious redirections, but use trusted antivirus apps for reliable threat detection.
Here are 7 ways to check if someone is using your SIM card:
If you enter the PIN (Personal Identification Number) code incorrectly several times, the SIM card will be locked. You need the PUK (Personal Unblocking Key) code to unlock the device.
Entering Incorrect PIN: If you enter the PIN (Personal Identification Number) for your SIM card incorrectly multiple times, your SIM card might get locked. Security Measures: Some mobile carriers or devices have security measures that automatically lock the SIM card if unauthorized access is detected.
Unusual sounds or echoes during calls
If you're noticing weird clicking sounds or high-pitched hums on multiple calls across different locations and with different people, it could be a sign that someone is eavesdropping or tracking your calls.
Cybercriminals can also use a hacked SIM card to receive or monitor your calls and texts. They could sit in the shadows and wait to uncover sensitive information that they can use to scam or blackmail you.
To check if your phone is hacked, look for signs like rapid battery drain, unexpected data spikes, new apps you didn't install, strange pop-ups, slow performance, or weird noises on calls, then use reputable antivirus software, check your account activity, and dial codes like *#21# to see if calls are being forwarded, taking steps like changing passwords and resetting to factory settings if needed.
Start by deleting unknown apps, updating your software, and running a security scan. Change passwords to any affected accounts and turn on 2FA. If you believe your phone has been hacked, start by removing any suspicious apps, updating your phone, and getting access back to any hacked accounts.
Press *#*#4636#*#* or *#*#197328640#*#* to see if anyone is watching your movements. These are Utility Net Monitor Codes. Dialing these codes can tell you if you're being tracked or monitored through your mobile phone.
What Does ##002# Really Do? 🔐📞 ##002# instantly cancels all call forwarding on your phone — busy, unreachable, or no-answer. It's a simple way to reset settings and protect your privacy.
Many cell phones sold in the United States contain software that prevents them from being used on different mobile networks even when those networks are technologically compatible. This software "locks" the phone to a provider's network, preventing it from being used on another company's network.
When a block is put in place, it is put on the phone's IMEI (the number to individually identify each phone). This means that when someone inserts a SIM card in the phone and attempts to use it, the phone will not be able to join a network and therefore won't work.
Why do SIM cards stop working? If you notice that you suddenly no longer have a signal on your phone, it could just be your provider facing technical issues. But your SIM card could also be at fault, so you should carefully remove and inspect it for: Physical damage.
A PUK (Personal Unlocking Key) is an 8-digit code that unlocks your SIM if the PIN has been entered incorrectly three times.
If you enter your PIN (Personal Identification Number) code incorrectly several times, the SIM card is locked. You then need the PUK (Personal Unblocking Key) code to unlock the device. The PIN and PUK codes are used to protect your subscription and device against unauthorised use.
For Android (Samsung, Pixel, Motorola and others)