Short answer
Before your old number stops working, add the new number to your accounts while you can still receive codes on the old one — and only then remove the old number. Start with your email, then Apple or Google, your bank, WhatsApp (Settings → Account → Change number, which moves your chats and tells your groups) and social media. Numbers are recycled: Princeton researchers found that 171 of 259 recycled US numbers were still linked to accounts at sites such as Google, Amazon or PayPal, so whoever gets your old number could receive your reset codes. Where you can, move two-step verification to an authenticator app or a passkey and keep backup codes. If the old number is already gone, use each service’s account recovery.
Why an old number is a risk
Carriers give disconnected numbers to new customers. Accounts that still list your old number will keep sending sign-in codes and password-reset texts to it — and to whoever has it now.
| Finding | Figure |
|---|---|
| US numbers disconnected each year | About 35 million, typically reassigned |
| Recycled numbers still linked to accounts at Amazon, AOL, Facebook, Google, PayPal or Yahoo | 171 of 259 |
| Numbers linked to email addresses exposed in data breaches | 100 of 259 |
| Numbers still receiving sensitive calls or texts, such as passcodes, within a week | 19 of 200 |
Update in this order
| Account | Where | Watch out |
|---|---|---|
| 1. Email (Google) | Google Account → Security → recovery phone, and the phones listed under 2-Step Verification | Change both — the recovery phone and the sign-in phone are separate settings |
| 2. Apple Account | Settings → your name → Sign-In & Security → Two-Factor Authentication, or account.apple.com | Add the new trusted number first, then delete the old one — you need at least one trusted number |
| 3. Bank and payment apps | In the app, or with your bank directly | Payment confirmations often go by SMS; some banks need a branch visit or a call |
| 4. WhatsApp | Settings → Account → Change number, on your main phone | The new number must receive SMS or calls and the old one must still be registered; your chats and groups move over |
| 5. Social media and the rest | Instagram and Facebook: Accounts Center → Personal details → Contact info; elsewhere, account or security settings | Remove the old number as a login method, not just as contact info |
Keep the old SIM working until you have finished, if you can — every change above may send a confirmation code to the old number.
Make the next change painless
- Switch two-step verification away from SMS where possible: an authenticator app or a passkey doesn’t depend on your number. See setting up two-factor authentication.
- Save backup codes for Google and other accounts somewhere safe; Google lets you sign in with them when you can’t get a code.
- Add a second recovery option — a recovery email, a second trusted number, a recovery contact — so one lost number never locks you out.
- Keep a list of the services that use your number; it makes the next change a ten-minute job.
If you have already lost the old number
- Try another way in first: backup codes, an authenticator app, a trusted device or a passkey.
- Ask your provider whether the number can still be restored — numbers are not reassigned immediately; the study cites a minimum waiting period of 45 days under US rules.
- Use each service’s recovery process: see Google account recovery without a phone and lost access to two-factor authentication.
- WhatsApp: without the old number you can’t use Change number; register the new number and restore from a backup if you have one.
Getting someone else’s codes on your new number?
A recycled number can still receive the previous owner’s texts and calls — including passcodes. Never use them: delete them and, if one service keeps writing, tell that service the number isn’t linked to you. And if a sign-up says your new number is “already in use”, it may still be attached to the previous owner’s account; contact that service’s support rather than trying to recover an account that isn’t yours. This is different from a SIM swap, where an attacker steals a number that is still yours.
Frequently asked questions
How long before my old number is given to someone else?
It depends on the carrier and the country. The Princeton study cites a minimum waiting period of 45 days under US rules; ask your provider before you cancel.
Will I lose my WhatsApp chats if I change number?
Not if you use Change number: WhatsApp moves your profile, individual and group chats and settings to the new number, deletes the old account and notifies your groups.
Should I keep SMS for two-step verification?
Prefer an authenticator app or a passkey, and keep your phone number only as an up-to-date backup recovery option.
I can’t receive codes on my old number any more. What now?
Use backup codes, a trusted device or an authenticator app if you have them. Otherwise start each platform’s account recovery, and ask your provider whether the old number can still be restored.
Sources: Princeton University — security and privacy risks of number recycling, Google Account Help — set up recovery options, Apple Support — trusted phone numbers and trusted devices, WhatsApp Help — about changing phone numbers, Google Account Help — sign in with backup codes