When Elizabeth ‘Kandi, a UK-based Nigerian medical doctor, took to X in May to share her friend's troubling experience, her post stirred public concern.
Her friend had fallen victim to a little-known yet potentially devastating loophole: inactive Nigerian phone numbers linked to bank accounts being recycled by telecom providers putting users’ financial data at risk.
The problem began when her friend’s Nigerian mobile line went unused for an extended period. Eventually, the telecom provider deactivated and recycled the number, assigning it to a new user who bought a fresh SIM card.
Unfortunately, the new owner gained access to the previous user’s bank account via USSD (Unstructured Supplementary Service Data) without needing authentication like a PIN or OTP.
Telecom Operators and SIM Recycling
In Nigeria, major telecom providers—including MTN, GLO, Airtel, and 9mobile—are permitted to recycle dormant numbers. According to guidelines issued by the Nigerian Communications Commission (NCC) in 2024, any phone number that remains inactive for six months—meaning it does not generate revenue through calls, SMS, data usage, or USSD—can be deactivated. After another six months of inactivity, the number becomes eligible for recycling unless a service disruption prevents its use.
Of the major networks, only MTN responded to a media inquiry from the Foundation for Investigative Journalism (FIJ). The provider confirmed that once a dormant SIM is deactivated and reassigned to a new user, the previous owner cannot reclaim it. MTN also clarified that they do not accept responsibility for any unauthorized financial activity stemming from such recycled numbers. They advise customers to notify their banks immediately when abandoning a phone number to avoid data breaches.
“If a customer fails to inform their bank about a deactivated number, MTN cannot be held liable for any financial loss arising from misuse of the recycled line,” MTN stated in an email.
A Widespread Risk for Nigerian Bank Customers
Beyond Kandi’s friend, other Nigerians have shared similar harrowing experiences. FIJ’s investigations revealed that some new SIM users began receiving transaction alerts intended for the former owners of their numbers. In more severe cases, unauthorized individuals used these recycled lines to siphon funds from the linked bank accounts.
One such victim, Ayomi (surname withheld), described how she lost ₦100,000 in March 2023 after her old line, still tied to her GTBank account, was reassigned to another user. Though the bank eventually refunded the money in two installments over eight months, the stress and vulnerability she faced led her to change her phone number and ATM card details.
In 2020, the dangers of SIM recycling drew national attention when Anthony Okolie was arrested by the Department of State Services (DSS) for unknowingly purchasing an MTN SIM previously used by a daughter of then-President Muhammadu Buhari. While Okolie was later released, the case underscored the potential for mistaken identity or unjustified suspicion due to reused phone numbers.
Why Do Telecom Companies Recycle Numbers?
A source at the NCC explained that phone numbers are a finite resource governed internationally by the International Telecommunication Union (ITU) under Recommendation E.164. These numbering plans ensure that every phone number adheres to a standard format, which restricts the number of usable combinations available.
"Because numbering resources are limited, telecom operators must manage them efficiently to ensure access and fair usage," the NCC insider reveals.
The NCC distributes number ranges to mobile and fixed-line operators to promote innovation and ensure consumer protection. While recycling is a necessary practice, the source acknowledged that the process lacks adequate safeguards to prevent abuse.
“The real issue arises when previous users fail to unlink their financial or personal services from old numbers, thereby exposing themselves to fraud,” the NCC source added.
Lack of Safeguards
A critical flaw in the current system is the absence of protocols to sanitize or purge old user data before a recycled SIM is reissued. Since many Nigerian services including banking, digital identity (NIN), and verification systems (BVN) are tightly tied to phone numbers, reassigned SIMs become a backdoor into someone’s personal and financial life.
In cases like Kandi’s friend, perpetrators used the recycled number to perform USSD transactions that didn’t require a PIN. Where an OTP was necessary, it was sent directly to the number now in the hands of the unauthorized user completing the breach.
What Can Be Done?
Telecom providers offer premium services to customers who plan to travel abroad or stay away from their lines for extended periods. These services allow subscribers to retain their numbers and keep them active—typically for a year or more. MTN and Airtel offer retention plans that can last up to three years, while GLO limits it to 365 days. However, many Nigerians remain unaware of these options.
In response to rising concerns, the NCC is now working on a cross-sectoral solution. The commission, in collaboration with the Central Bank of Nigeria (CBN) and security agencies, is piloting a data-sharing platform designed to track recycled numbers and flag any associated with fraudulent activity. Once launched, this system would be accessible to financial institutions, telecom providers, and other stakeholders to prevent misuse of reassigned lines.
“Our goal is to protect consumers by ensuring that when a number changes hands, it doesn’t compromise the integrity of services linked to the old owner,” the NCC source said.
Recommendations for Users:
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Immediately inform your bank and other service providers if you change or stop using your phone number.
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Consider retention services from your telecom provider if you plan to leave the country or go offline for extended periods.
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Regularly check which services are linked to your number and update contact details where necessary.
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Monitor bank and SMS alerts to detect unauthorized transactions early.
As digital life increasingly depends on mobile connectivity, Nigerians must remain vigilant about the hidden risks associated with something as seemingly harmless as an inactive phone number.
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