Cancelling a Singapore mobile number

Unlink everything while you can still receive OTPs.

Your number will be recycled and given to a stranger. Anything still linked to it — WhatsApp, PayNow, SMS 2FA — is what that stranger can receive or claim. Do these steps in order, before you cancel the line.

Golden rule: keep the SIM active until every step is done. Once the line is cut, OTP-gated removals become impossible.

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1.Prepare

Have your landing spot ready before touching anything.

Have your new number (or decide you will go number-free)
Most updates below ask you to verify a replacement number by OTP. Get the new SIM working first.
Install an authenticator app
Google Authenticator, Authy or a password manager with TOTP. You will move SMS 2FA here so codes no longer depend on any phone number.
Build your list: search your inbox and SMS history
Search email for "verification", "OTP", "phone", "2FA". Scroll your SMS inbox — every sender there (bank, ride app, Google, clinic) is an account linked to this number.

2.Move 2FA off SMS first

This is the step people skip, and the one that locks them out. If you remove the number before replacing 2FA, some accounts become unrecoverable.

Google: replace SMS 2FA and recovery phone
myaccount.google.com → Security → 2-Step Verification: add authenticator or passkey, then remove the old number. Also check Personal info → Phone, and Security → Recovery phone — they are separate.
Removing the number in one place does not clear it everywhere in Google.
Google account
Apple ID: update trusted phone number
Settings → [your name] → Sign-In & Security → add the new number as trusted first, then remove the old one. Apple requires at least one trusted number.
Apple ID
Microsoft: security info
account.microsoft.com → Security → Security info. Replace the old phone with authenticator or the new number.
Microsoft account
Everything else that texts you codes
Work SSO, GitHub, crypto exchanges, brokerages, admin portals. Switch each to authenticator app or passkey, save backup codes, then remove the old number.

3.Money and identity (Singapore)

Banks and government services are the highest-stakes leftovers.

PayNow: deregister or move the mobile proxy
In your bank app, delete the PayNow mobile profile or update your registered mobile — the old proxy then drops off automatically. Otherwise money sent to your old number goes to a stranger (or theirs to you).
DBS/POSB steps
Every bank and card: update registered mobile
Change the mobile number in each bank app, then confirm SMS OTPs now go to the new number. Do this per bank — they do not share updates.
Singpass: update mobile
Update your registered mobile in the Singpass app or portal. If Singpass OTP still goes to the old SIM after cancellation, account recovery gets painful.
Singpass
Grab, Foodpanda, Shopee, Lazada, Carousell, transit and telco apps
Profile → change mobile, complete OTP on the new number. These accounts hold payment methods and order history.

4.Social and email recovery

Less urgent than money, but they let strangers reset your passwords.

Facebook, Instagram, TikTok, X: remove or replace the number
Settings → personal/contact info on each. Remove the old number or swap it for the new one.
Email accounts: recovery phone
Any mailbox (not just Gmail) that uses this number for recovery. If a stranger can SMS-reset your email, they can reset everything else.

5.Messaging apps — do these last

Messaging apps are identity, and the switch is one-way. Do them after everything above, while the old SIM still receives SMS.

WhatsApp: use Change number (or Delete account)
Keeping WhatsApp: Settings → Account → Change number — this migrates chats and deletes the old-number account. Leaving WhatsApp: Settings → Account → Delete my account. Uninstalling the app does NOT deregister the number.
Uninstalling is not deregistering. The account stays claimable on the old number.
WhatsApp: changing numbers
Telegram: Change Number, or delete the account
Keeping Telegram: Settings → tap your number → Change Number. Leaving: use the deactivation page. Inactive accounts otherwise linger for months and are claimable by the next SIM owner.
Telegram deactivation
Signal, Viber, WeChat, LINE, WhatsApp Business
Each has its own change-number or delete-account flow in settings. Same rule: uninstalling leaves the number registered.

6.Quiet period, then cancel

The SIM itself is your final audit tool.

Keep the SIM for 1–2 weeks and watch every SMS
Each unexpected OTP, bank alert or app message is an account you missed. Update that account, then keep waiting. A quiet week means you are done.
Cancel the line
Only now tell the telco to terminate. Whatever is still linked after this is what the next owner of your number inherits.

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