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The short answer
SIM swap fraud happens when a criminal gets your mobile network to move your number onto a SIM they control, so your SMS codes and USSD access go to them. The first sign is usually your phone suddenly losing signal or showing 'SIM not registered'. Call your network from another phone at once, then your bank, and ask both to block the line and your accounts until you are back in control.
How SIM swap fraud works
Your phone number is a key to your money. Banks send one-time codes to it, USSD banking works through it, and many apps use it to reset passwords. If a fraudster gets a replacement SIM issued in your number, all of that moves to their phone.
They usually start with your personal details, gathered from phishing, data leaks, social media or a fake call. Then they approach a network outlet or agent pretending to be you, or bribe an insider. Once the new SIM is active, your old one goes dead, and they use your number to receive codes, dial your bank's USSD code or reset your banking app.
What the NCC requires
The Nigerian Communications Commission (NCC) has SIM Replacement Guidelines. It says verification with your National Identification Number (NIN) is compulsory for a SIM replacement, in addition to the other checks in the guidelines, and that replacements must be done by networks or their licensed agents in a controlled environment. The NCC also warns people never to share the one-time password (OTP) sent when a SIM is activated, especially after a replacement, because fraudsters ask for it.
These rules make SIM swaps harder, but not impossible. Your own habits still matter.
Why your phone number is worth so much
In Nigeria the phone number does more work than in many countries. It is tied to your NIN, it is usually the number on your BVN record, it receives your bank alerts and codes, and for millions of people it is the only way they bank, through USSD. A fraudster who holds your number can often do three things in quick succession: receive a code to reset your banking app, approve a transfer with a code sent by SMS, and dial your bank's USSD code to move money if your USSD PIN is weak or known. That is why speed matters so much when your line goes dead, and why moving away from SMS codes, where your bank or app allows it, removes much of the risk.
Look after the details a fraudster needs to pass as you. These are typically your full name, date of birth, address, phone number, NIN and BVN, plus answers to security questions such as your mother's maiden name. Most of them leak through over-sharing online and through fake forms and calls.
Warning signs
- Your phone suddenly shows no service, 'SIM not registered' or emergency calls only, while people around you on the same network have signal.
- You get a text saying your SIM has been replaced or a SIM change was requested, which you did not ask for.
- Someone calls asking you to read out a code that just arrived, often claiming to be from your network or bank.
- You stop receiving bank alerts or calls.
- You get emails or app notifications about password changes you did not make.
What to do immediately
- Borrow another phone and call your network's customer line. Ask whether a SIM replacement was done and ask them to block the line.
- Call your bank's fraud or customer line, explain a SIM swap may have happened, and ask them to block your accounts, cards and USSD access.
- From a safe device, change your email and banking app passwords.
- Check your account history for transfers you did not make, and list them.
- Report to the police. The Nigeria Police Force National Cybercrime Centre (NPF-NCCC) handles cybercrime. Our guide to reporting fraud covers what to bring.
- Follow the rest of our first-hour fraud plan.
How to make yourself a harder target
| Step | Why it helps |
|---|---|
| Use an authenticator app instead of SMS codes where offered | Codes stay on your device, not your phone number |
| Never share codes sent to your phone | Fraudsters need them to finish a swap or a transfer |
| Keep your NIN, BVN and date of birth off social media | They are the details used to impersonate you |
| Set a USSD PIN that is not your birthday | Slows a fraudster who gets your number |
| Keep bank alerts on email as well as SMS | You still hear about debits if your line is taken |
Our article on authenticator apps vs SMS codes explains why codes sent by text are the weak point, and USSD banking fraud covers the risk to *code banking specifically. For your BVN, see is it safe to share your BVN.
Worked example
Example only. Funmi's phone loses signal at 9 pm. Her husband's phone, on the same network, is fine. She calls the network from his phone and learns a replacement was done an hour earlier. She calls her bank, which blocks her account and USSD access. When she checks the next morning, someone had tried a ₦250,000 transfer that failed because the account was already blocked.
Where Pryme fits
Pryme does not use SMS codes. Sign-in and approvals use an authenticator app plus your transaction PIN, so taking over your phone number alone does not give someone access to move money from your Pryme account. See security for details.
Questions people ask
How do I know if my SIM has been swapped?
Your phone suddenly loses all signal or says the SIM is not registered, while others on your network have service. Call your network from another phone straight away.
Can a SIM be replaced without my NIN?
The NCC says NIN verification is compulsory for SIM replacement. Fraud can still happen through impersonation or insiders, so act quickly if your line goes dead.
Will my bank refund money lost to SIM swap fraud?
It depends on the investigation, including how fast you reported and whether you shared codes. Report immediately and keep every reference number.
Should I stop using USSD banking?
Not necessarily, but set a strong USSD PIN, keep limits low, and know how to block it quickly through your bank.
Sources
- NCC: NCC demands MNOs, agents, consumers comply with SIM Replacement Guidelines · accessed Oct 2026
- NCC: Guidelines on SIM Replacement · accessed Oct 2026
- NCC: Frequently asked questions on NIN and SIM integration · accessed Oct 2026
- US FTC: SIM swap scams, how to protect yourself · accessed Oct 2026
- Nigeria Police Force National Cybercrime Centre (NPF-NCCC) · accessed Oct 2026
This article is general information, not financial, legal or tax advice. Products described are provided under the terms on this site and are subject to regulation and eligibility.