Changing your phone number may feel like leaving the old one behind, but disconnected numbers can eventually be assigned to someone else — making it important to disconnect your number from online accounts before giving it up.
A phone number can become part of a person’s identity.
It follows us through text messages, bank accounts, social media profiles, online shopping, medical appointments, work contacts and countless forms asking for a number where we can be reached.
But unlike a Social Security number, a cellphone number generally does not belong to one person forever.
When someone cancels a wireless line or gives up a telephone number, the number does not necessarily disappear. After sitting unused for a period of time, it can eventually return to circulation and be assigned to somebody else.
That creates an unusual situation in the digital age: the new owner of a phone number may inherit calls and text messages intended for a person they have never met.
More importantly, the previous owner may have left that number attached to online accounts.
Phone Numbers Are Recycled
There are only so many telephone numbers available within the North American Numbering Plan, which covers the United States and several other countries and territories.
Rather than permanently retiring every number after a customer stops using it, telecommunications providers can eventually make disconnected numbers available for reassignment.
Federal Communications Commission rules establish a minimum waiting — or “aging” — period before that can happen.
Under FCC rules, a permanently disconnected telephone number cannot be reassigned for at least 45 days after disconnection.
The rule was adopted in part because reassigned numbers can create problems for both consumers and businesses. A company may continue calling or texting a customer without realizing that the number now belongs to someone else.
The FCC has also established a Reassigned Numbers Database designed to help callers determine whether a number has been permanently disconnected and potentially reassigned.
The database is intended to reduce calls meant for previous subscribers.
But the 45-day federal minimum does not mean every telephone number will automatically be handed to another person on day 46. It establishes the minimum period before reassignment is permitted.
A number could remain unused longer depending on the provider and circumstances.
Your Old Number Could Eventually Belong to a Stranger
Imagine changing your cellphone number after using it for 10 years.
Friends and family learn the new number. Your contacts are transferred to your new phone, and eventually the old number fades from memory.
Months later, another customer could potentially receive it.
That person has not received your old phone, photographs, contacts or text-message history simply because they received the number.
The number itself, however, may still exist in places you forgot about.
A restaurant reservation account could have it.
A retailer’s loyalty program could have it.
An old social media account could have it.
So could a bank, email account, doctor’s office, payment service, delivery company or website you joined years ago.
If those organizations are not told that your number changed, they may continue attempting to reach you at a number that now belongs to somebody else.
That is one reason changing a telephone number should involve more than simply activating a new line.
The Bigger Concern Is Account Security
Phone numbers increasingly serve a second purpose beyond making calls.
They are also used to prove who we are.
Many websites send one-time security codes through SMS as part of two-factor authentication. Others allow customers to use a telephone number to recover an account or reset a forgotten password.
That makes an outdated number particularly important to remove.
The Federal Trade Commission specifically advises consumers who are not keeping their telephone number to update the number associated with accounts and services that use it to identify them.
Consumers should pay particular attention to accounts containing sensitive personal or financial information.
That can include email accounts, banks and credit cards, social media accounts, payment apps, online retailers, cloud storage and other services where a telephone number is used for account recovery or authentication.
The FTC recommends using two-factor authentication to strengthen account security but notes that SMS verification has drawbacks. When available, the agency says an authenticator app or physical security key provides stronger protection than text-message verification.
A New Number Doesn’t Give Someone Your Old Phone
There is also an important distinction between giving up a telephone number and giving up a physical device.
Receiving somebody’s former number does not automatically give the new subscriber access to the previous subscriber’s photos, contacts, apps or stored text messages.
Those are separate from the telephone number.
Selling, donating or trading in a physical smartphone creates its own privacy considerations.
The FTC recommends backing up personal information before disposing of a phone, removing SIM and SD cards when applicable, disconnecting accounts and trusted-device relationships, and erasing personal information by restoring the device to factory settings.
Consumers keeping their physical phone but changing only the number face a different task: finding everywhere the old number is still being used.
Don’t Forget About Account Recovery
One of the easiest places to overlook an old telephone number is an account’s recovery settings.
Someone may use an email account every day without realizing that the backup telephone number was entered five or ten years earlier.
That can become a problem later.
If the account detects unusual activity or the owner forgets the password, the service could attempt to verify the user’s identity using outdated recovery information.
The FTC recommends checking account recovery information and making sure the listed telephone numbers and email addresses are current and accessible.
Consumers changing numbers may want to do this before disconnecting the old line, while they can still receive verification codes sent to it.
What About the National Do Not Call Registry?
Changing telephone numbers can even affect something as seemingly unrelated as the National Do Not Call Registry.
According to the FTC, consumers who move and receive a new number need to register that new telephone number if they want it included on the registry.
Consumers do not need to manually remove their former number. The FTC says numbers are automatically removed when they are disconnected and reassigned.
That illustrates just how much infrastructure exists behind something most consumers rarely think about.
To the user, a phone number can feel permanent.
To the telecommunications system, it is a resource that can eventually be used again.
You May Be Able to Keep Your Number Instead
Giving up a familiar number isn’t always necessary simply because someone wants to change wireless companies.
Federal number-portability rules generally allow consumers who switch service providers while remaining in the same geographic area to keep their existing telephone number.
The process is commonly known as “porting.”
For someone who has used the same number for years, porting can avoid the considerable task of updating friends, family members, employers and dozens of online accounts.
Consumers considering a carrier change may therefore want to determine whether they can transfer their existing number before canceling service.
What Should You Do Before Giving Up a Phone Number?
The safest time to deal with an old number is before it becomes an old number.
Before disconnecting a line, consumers should review the accounts that matter most and replace the number while they can still receive calls and verification codes.
Start with email, banking, credit cards, payment apps, social media and other accounts that could be used to recover passwords or verify identity.
Then consider less obvious places: healthcare portals, retailers, delivery services, loyalty programs, subscription accounts, insurance companies, utilities, schools and professional accounts.
It is also worth searching email for phrases such as “phone number,” “verification code,” “two-factor authentication” or the old number itself. Those searches may uncover accounts that have been forgotten.
Where an account offers stronger authentication methods, consumers can also consider moving away from SMS verification and using an authenticator app or security key.
Finally, tell important contacts that the old number will no longer belong to you.
Your Number Is Personal — But Not Necessarily Permanent
For years, a phone number can function almost like a digital address.
People know how to reach you there. Businesses recognize it. Websites use it to verify you. Friends may have it saved without ever thinking about whether it could change.
That familiarity can make a number feel like something we own permanently.
The telecommunications system works differently.
Once a number is permanently disconnected, federal rules require a waiting period before it can be reassigned, but the number can eventually return to circulation.
Someday, a stranger may answer calls to a number that friends once associated with you.
