What Happens to Your Old Phone Number When You Change It

Key takeaways

• When you give up a phone number, it is usually recycled: after a waiting period, the carrier assigns it to a new customer.
• In the US, that waiting period is at least 45 days under FCC rules. After that, a stranger can hold your old number.
• Any account that still lists the old number can send its sign-in and password-reset codes to the new owner.
• Before you change numbers, update every account, move two-factor sign-in to an authenticator app or passkey, and only then let the old number go.

When you change your phone number, the old one doesn't retire. It becomes a recycled phone number: your carrier holds it for a while, then gives it to a new customer. Your accounts don't know that happened. Any service that still has the old number on file will keep sending calls, alerts and one-time codes to it, and now someone else receives them.

The fix is simple, but it has to happen in the right order. Update your accounts first, then give up the number. This guide covers how number recycling works, what the next owner can see, and a step-by-step checklist for switching. It applies to any number you stop paying for: a carrier line, a prepaid SIM, or a second number from an app such as 2Phon.

What happens to your old phone number?

Your old number goes back to your carrier, waits for a set period, and is then assigned to someone else. Phone numbers are a limited resource, so carriers reuse them. The FCC put it plainly when it set up its reassigned numbers database: "Millions of phone numbers are reassigned each year" (FCC news release, December 12, 2018).

The waiting period is called aging. In the US, the rule is in the FCC's numbering regulations: "Numbers previously assigned to residential customers may be aged for no less than 45 days and no more than 90 days." For business numbers, the range is 45 to 365 days (47 CFR § 52.15, checked 2026-11-11).

Two limits are worth knowing. First, these are US rules. Other countries set their own waiting periods, so check with your carrier. Second, the FCC's database exists so that businesses can check whether a number has changed hands before they call it. It reduces wrong-number calls. It doesn't update your accounts for you.

Can the new owner of your number get into your accounts?

Yes, if an account still sends its codes to that number. A code sent by SMS or voice call goes to whoever holds the number today. If your email, shop or social account still lists your old number for sign-in or password reset, the new owner can receive those codes.

Researchers at Princeton University measured how common this is. Kevin Lee and Arvind Narayanan sampled 259 phone numbers that two major US carriers were offering to new subscribers. They found that 171 of them were still tied to existing accounts at popular websites, "potentially allowing those accounts to be hijacked." And 100 of the 259 were linked to login credentials that had leaked online (Princeton recycled-numbers study, paper abstract, 2021).

They also kept 200 recycled numbers for a week to see what arrived. Nineteen of them, nearly 10%, received sensitive calls or messages meant for the previous owners, such as authentication passcodes and prescription refill reminders.

Most people who get a recycled number are just annoyed by the wrong calls. The risk comes from the few who aren't. With your old number, a new owner can:

• Reset passwords on accounts that use the number for recovery.
• Pass SMS two-factor sign-in if they also have your password, for example from a data leak.
• Receive your private notices, such as appointment reminders, delivery updates and bank alerts.
• Look you up. The Princeton team found that most available numbers also produced hits on people-search sites, which list details about previous owners.

This is a quieter cousin of the SIM swap scam. In a SIM swap, a criminal steals a number you still use. With recycling, you hand the number over yourself, and no one has to trick the carrier.

How to change your phone number without losing your accounts

Keep the old number working until every account is moved. Many services confirm a change by sending a code to the old number, the new one, or both. That is easy while you hold both and hard once the old one is gone.

1. Get the new number first

   Have the new number active before you give up the old one. A few days of overlap is enough for most people. A few weeks is safer.

2. List every account that knows the old number

   Go through your password manager, the apps on your phone, and your email (search for "verification code" and "welcome"). Don't forget your bank, tax or government portals, your doctor, your employer and delivery services.

3. Change the number in each account

   Start with the accounts that can reset others: your main email, your Apple Account or Google Account, then banks and payment apps. Confirm the new number with the code each service sends.

4. Move two-factor sign-in off phone numbers where you can

   Where a service offers an authenticator app, a passkey or a security key, switch to it. Those stay on your device and don't depend on any number. Save the backup codes.

5. Move your messaging apps

   Apps tied to a number have their own tools for this. WhatsApp, for example, has a Change number feature that moves your profile, settings and chats to the new number and deletes the account tied to the old one.

6. Tell people, then let the number go

   Give your contacts the new number. Check once more for stray accounts, and only then cancel the old line or subscription.

Where to change it on the big accounts

• Apple Account. On your iPhone, go to Settings, tap your name, then Sign-In & Security, then Two-Factor Authentication, and add the new trusted phone number. Apple's steps are in its guide to trusted phone numbers.
• Google Account. Open Security & sign-in, then Recovery phone, and edit the number. Google notes that "it may take up to 7 days for those changes to take effect," which is one more reason to start early (Google Account Help, checked 2026-11-11).
• WhatsApp. Use Change number inside the app instead of signing up again. WhatsApp describes what moves across in About changing phone numbers.

What if you already gave up the number?

Act now and assume the number will be reassigned. If you're still inside the aging period, you may have a few weeks before anyone else holds it.

What if you received a recycled number?

Expect some calls and codes meant for the last owner. You haven't done anything wrong. The previous owner simply left accounts and contacts pointing at the number.

• Don't use codes that aren't yours. Signing in to someone else's account with a code that reached you by accident is not harmless. Ignore it. Our guide to verification codes you didn't request explains what these messages mean.
• Tell real callers (a clinic, a school, a bank) that the number has a new owner, so they update their records.
• Block and report the rest. See how to stop spam calls for the iPhone settings that help.
• Messaging apps may show leftovers. WhatsApp says it treats a number as recycled when an account goes unused for 45 days and is then activated on a new device. In that case it removes the old account data, such as the profile photo (WhatsApp Help Center, checked 2026-11-11).

Does this apply to a second number too?

Yes. Any number you stop paying for can end up with someone else. That includes prepaid SIMs, numbers from apps, and short-lived numbers. The shorter a number's life, the more often this comes up, which is the main weakness of a burner number.

2Phon is an iPhone app that gives you a real second phone number from dozens of countries. You use it to receive verification codes when you sign up for apps and services, and to make and receive real calls. It keeps your personal number out of sign-up forms. It doesn't send text messages.

The number is persistent, but it is not permanent. It's yours to keep while your subscription is active. Under 2Phon's Terms, if you cancel, your subscription lapses or a payment fails, the number may be released and re-assigned to another user. So treat it like any other number:

• Before you cancel, run the same steps as above for every account that uses your 2Phon number.
• Keep your Apple payment method current, so a failed renewal doesn't end the subscription by accident.
• Don't make it the only key to your bank or main email. Those belong on an authenticator app or passkey, with a recovery number you expect to keep for years.

Used that way, a second number makes the next number change easier. Shops, marketplaces and dating apps only ever had the second number, so your main line has far fewer accounts to untangle. For help deciding which accounts go where, see which phone number to use for verification. If you want a separate number for sign-ups and calls, you can get 2Phon on the App Store.

For which accounts suit a second number in the first place, see should you use a second number for 2FA. Apps also differ in how long they let an unused number sit before taking it back, which we cover in free vs paid second number apps.

The short version

Your old phone number is recycled and handed to a new person, in the US no sooner than 45 days after you give it up. Whatever is still linked to it goes with it. Move your accounts first, switch your important logins to an authenticator app or passkey, and drop the number last. If you're still choosing how to split your numbers, start with what a second phone number is and what it's good for.