How to Set Up SIM Card Lock on Android and iPhone?

Mark Kreitzman
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March 30, 2022
Modified On
June 20, 2024

Introduction to SIM Card Lock

People don't bother with the SIM Card Lock in their phones, but it carries significant weight. You can set up a screen lock easily, but you may need to realize that there is another extra layer of security you can add, i.e., the SIM Card Lock, to secure your phone number. In this blog, I will discuss what SIM card lock is, how to set up a SIM card lock on Android and iPhone, and the pros and cons of setting up a SIM card lock on your phone.

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What Is A SIM Card Lock?

SIM Card Lock is a PIN that requires a lock screen PIN, Pattern, Fingerprint or Password, and a SIM Card to be active before you can unlock the phone. It is a physical two-factor authorization that disallows hackers from tracking or misusing your SIM Card.

Default SIM Pin Codes of Popular Mobile Carriers

Usually, a SIM comes with a default PIN code directly from your mobile carrier. These codes vary company by company. Here is the list of the defalut PIN code of some of the popular mobile carriers:

1. Default SIM Card Pin code of Sprint and T-Mobile is 1234.

2. Default SIM Card Pin code of AT&T and Verizon is 1111.

You can either Google these codes or call your carrier support and ask for the codes.

Pros and Cons of a SIM Card Lock on Mobile Phone

Pros of a SIM Card Lock

  1. If your phone is stolen or lost, someone can't pull your SIM out and put it in another phone to reset your application passwords or use your mobile service to impersonate you.
  2. The SIM lock will buy you some time to deal with your mobile service provider.

Cons of a SIM Card Lock

  1. It buys you time, but if the wrong person gets your phone and thus gets the IMSI # of your SIM card, that SIM card has a number that identifies the country, mobile operator, and the unique identifier of that SIM. Now they know what operator to call and can impersonate you to get the PUK code, which stands for Pin Unlock Key. Once unlocked, they can use your mobile service to access your applications or impersonate you.  
  2. Every time you reboot your phone, your SIM card will be locked and require you to enter a PIN, a small sacrifice to have security. 
  3. Locking your SIM with a PIN is no defense against a SIM swap. A SIM swap is where a nefarious person uses different tactics to get your operator to switch your service to connect to the SIM in the hands of the hacker, and your device is now out of the equation. The hacker can be thousands of miles away.  

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How to Set Up A SIM Card Lock on Your Smartphone?

How to Lock SIM Card on Android Phone:

Here is how to do the SIM card lock on your Android phone.

  1. Open "Settings" on your phone
  2. Now, go to "Security" and then "More Security Settings"
  3. Choose a SIM card lock.
  4. Toggle "lock SIM card"
  5. Enter SIM card PIN. Use the defualt PIN if you are locking for the first time.
  6. Done

Bonus Tip:

  1. If you want to change the Default PIN, click on Change SIM PIN.
  2. Add your old PIN, and then add your new PIN.
  3. Your PIN is changed. Write it down so you won't forget it.

Watch this video for more information:

How to Lock SIM Card on iPhone:

Here is how to do the SIM card lock on your iPhone.

  1. Go to settings
  2. Tap on "Mobile Service"
  3. Tap on SIM PIN.
  4. Toggle on SIM PIN if your phone has two SIM, then you may need to select a SIM, then select the SIM PIN option.
  5. Enter default PIN
  6. Done

Essential Things to Know Before Setting Up A SIM Card Lock

Wait to turn the SIM lock on. When you turn on the SIM lock, you will be asked for a SIM PIN. If this is the first time turning it on, it will ask you for a 4-digit default passcode and warn you that you usually have three attempts to get it right, or it will lock your SIM up. I'll give you instructions at the end later in the blog. I want to warn you before we take the next step.  

Each operator has a default passcode, usually 1111, 0000, or 1234. I googled this for AT&T and Verizon, and both said 1111, so on my phone, I used 1111, and it worked both times.   Now, if the SIM was locked previously and then unlocked using a PUK code, then the default PIN will change to 0000 for Verizon. So keep that in mind if your SIM was locked previously and google your carrier's default PIN after a PUK unlock. 

If you make two attempts and fail, then bail out of the PIN lock feature and contact your provider before that 3rd attempt, or you won't be able to use your cell phone to contact them.  

So let's move forward and turn on the SIM lock. Enter the default 4-digit passcode, which will confirm the lock is correct. You can now change the SIM pin. Otherwise, the SIM lock has no value, as a hacker would enter the default passcodes to try and access it.  

Once you change your SIM lock PIN, you're now set, and if someone gets a hold of your device and removes the SIM, it will not be usable on another device. This SIM PIN differs from the PIN you would enter to unlock your phone, so choose a lock number you will remember.

Now, if you ever forget your SIM lock code, you can still unlock it with a PUK code, a PIN Unlock Key different for every SIM card.   Sometimes You can find the PUK on the original SIM card if you still have the business card-sized piece of plastic, or you can call your service provider and request the PUK, which can take some time for them to provide, but when you get the PUK you can unlock your SIM and start over.  


Again, the SIM card lock only helps when someone has physical access to your device. One of the fastest-growing threats to your mobile is an actual SIM swap which can be done remotely by hackers who impersonate you, bribe a carrier employee, or plant their people within a carrier or 3rd party store employee. If you want to secure yourself against SIM swaps and SIM swap losses, check out the secure mobile SAFE plan at where your account is protected from SIM swaps and the release of your PUK to nefarious people. 

Also, Read: How Do I Know If My Phone Is Unlocked?

Mark Kreitzman
General Manager, Efani Secure Mobile

I am General Manager at Efani Secure Mobile. I have over 20 years of experience in enterprise cybersecurity, including 8 years focused on mobile security. I have a high level of achievements and expertise in the Service Provider Alliance/Partner space. I am positioned at senior levels with SPs/Resellers such as AT&T, Verizon, Cisco Systems, and many others. I have deep experience in SaaS, cybersecurity, telecom, mobile & blockchain.

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