Secure your phone: Easy steps to lock a SIM card on Android and iPhone

In an era where your mobile phone number is the key to your digital life, including bank accounts and social media verification, securing your SIM card is a cybersecurity imperative.

In an era where your mobile phone number is the key to your digital life, including bank accounts and social media verification, securing your SIM card is a cybersecurity imperative.

The rise of sophisticated scams, particularly SIM swapping, has made millions of users vulnerable. A SIM swap attack involves a fraudster tricking your mobile network provider into transferring your phone number to a SIM card they control. Once they have your number, they can intercept sensitive one-time passwords (OTPs) and reset your accounts, leading to devastating financial loss or identity theft.

Adedeji Olowe, founder of Lendsqr and board leader at Paystack, breaks down the financial sequence used by criminals:

“They take your SIM card and try to check all the banks to see which banks you [use]. [They can dial a code] to see your BVN. When they do that, even if you don’t have any money, they will check your account number, then try to reset, download your Internet bank and log in again. The problem starts from somebody having access to your SIM card.”

Not knowing how to lock a SIM card is one of the biggest hurdles to national cybersecurity. As Terseer Saror, Principal Manager at the Nigerian Communications Commission (NCC), notes, “There’s just a lack of awareness… on the fact that you could actually even block your SIM card, first things first, then on the for those that actually know how to go about it.” 

When most people think of phone security, they think of the screen lock: the fingerprint, face ID, or pattern/PIN they use to unlock the device itself. This is critical, but it doesn’t protect the SIM card.

SIM card locking, also known as setting a SIM PIN, is a separate security feature.

When you enable a SIM PIN, the following happens:

Learning how to lock a SIM card is arguably the most effective way to thwart a SIM swap attempt, as it renders the stolen or swapped SIM inoperable in the new device.

The exact menu path can vary slightly based on your phone’s manufacturer (Samsung, Google, Xiaomi, etc.) and the Android version, but the core steps remain the same.

The standard process:

The standard process:

Your iPhone SIM is now protected. This PIN will be required every time the device is powered on or the SIM is moved to a new phone.

You have only three attempts to enter the correct SIM PIN. After the third incorrect attempt, your SIM card will be temporarily locked and you will be asked for a PUK (PIN Unlocking Key) code.

While setting a SIM PIN is the primary way to prevent unauthorized use, if your phone or SIM is stolen, you must act fast to protect your network line. Saror says your mobile network provider (MTN, Airtel, Glo, etc.) can issue a permanent block on the line. The owner of a stolen SIM card “can walk into any of the offices, or website, of their network provider to lock the SIM.”

Contact your network’s customer care immediately via a different phone or their official social media/web channels. You will need to verify your identity (usually with your full name, registered ID number, and possibly the SIM’s PUK code).

This official line block ensures that even if a fraudster bypasses your SIM PIN (e.g., via the PUK code), the SIM is rendered completely useless on the network.

Learning how to lock a SIM card on your device is a small action with a massive impact on your cybersecurity posture. It protects the integrity of your mobile number, which acts as the digital anchor for your most sensitive accounts.