Here’s a practitioner-style explainer on the Lost SIM Card Block Procedure under the Philippine SIM Registration Act (RA 11934) and common carrier/NTC practice. This is general information—not legal advice for your exact facts.

1) The essentials in one glance

Law in play: SIM Registration Act (RA 11934) + IRR; enforced by NTC/DICT and implemented by public telecommunications entities (PTEs: Globe, TM, Smart, TNT, DITO, etc.).
Goal when your SIM is lost/stolen: (1) Immediately disable the SIM/number to stop OTP hijack and fraud; (2) safeguard your identity data in the SIM registry; (3) replace the SIM/number properly.
Who can request a block? The registered subscriber (or lawful representative with proof). For minors, the parent/guardian that registered the SIM. For corporate SIMs, the authorized company representative.
Blocking what, exactly? You can (A) suspend or terminate the SIM/number, and (B) ask to flag the account in the SIM Registry. Blocking the SIM does not block the phone—IMEI blacklisting is separate.

2) Immediate step-by-step when a SIM is lost or stolen

Secure your accounts (first 10–30 minutes)
- Turn on account lock / “lost mode” for your device if available (Find My / Find My Device).
- Change passwords for email, bank/e-wallets (GCash, Maya), social media; enable/rotate 2FA away from SMS (use app-based authenticators).
- Unlink the number from critical services where possible and add “SIM lost” notes to account help centers.
Request carrier block/suspension (ASAP)
- Use the carrier’s hotline, official app/portal, or store. State it’s a lost/stolen SIM, request immediate outgoing and incoming block, and ask to flag the SIM registration record.
- Provide number, full name, birthdate, address, valid ID details you registered, and last top-up/bill info for verification.
- Ask for a reference/ticket number and whether the block is temporary suspension (reversible) or permanent deactivation.
(Optional but helpful) Affidavit & police blotter
- Many PTEs do not require an affidavit for temporary suspension; some require it for permanent deactivation or SIM replacement if verification is borderline.
- If there’s wallet/OTP fraud, file a police blotter (this helps banks/e-wallet chargeback and NTC/LEO escalation).
Request number replacement or SIM swap (once identity is verified)
- Ask for a replacement SIM/eSIM with the same number (MNP-ported numbers are also replaceable—but you may be routed to your current network).
- Bring government ID(s), SIM registration details, affidavit if required, and corporate authority if company-owned.
- For eSIM, expect QR re-provisioning and device checks. For roaming users, PTEs may require video KYC or notarized SPA.
Consider device/IMEI blacklisting (if the phone is missing)
- Report the IMEI to your carrier and NTC for blacklist so the handset can’t attach to local networks. You’ll need the IMEI(s) (box/receipt, Google/Apple account, or invoice) and proof of ownership.
Alert high-risk services
- Notify GCash/Maya/bank support that the SIM tied to your account was lost; request freeze or 2FA reset.
- If you used the number for government e-services (PhilHealth, SSS, LTO, DICT-Trace history, etc.), update contact numbers.

3) Your rights under the SIM Registration Act (what you can insist on)

Right to block/suspend your SIM promptly upon report of loss/theft.
Right to replacement of the same number after successful re-KYC, subject to carrier procedures/fees.
Right to data protection: Your registration data is confidential, used only for lawful purposes (fraud/LEO requests with formal process).
Right to be informed: Get a ticket/ref number, the type of block placed, and next steps for reactivation/replacement.
Right to redress: If the carrier unduly delays or refuses a block/replacement despite proper compliance, you may escalate to NTC (consumer protection/complaint) and seek damages for losses proximately caused.

4) What the carrier is allowed (and required) to do

KYC verification before acting on a block or swap (to prevent SIM-swap fraud). Expect multi-factor checks (ID, selfies/video KYC, last load/transaction, security questions).
Immediate bar on voice/SMS/data on request; carriers generally keep internal audit logs of your request time.
Registry flagging so the lost SIM cannot be re-registered by another person.
Disclosure to law enforcement only with proper legal process (subpoena/court order) or in exigent threats to life scenarios permitted by law.

5) Special situations & how to handle them

Mobile Number Portability (MNP): If your number was ported, the receiving/current network handles the block and replacement. Tell the hotline if your number is ported.
Corporate/Company lines: Only the authorized signatory can request blocks/swaps. Employees should report to IT/Telecoms Focal immediately.
Minors: The parent/guardian who registered the SIM makes the request.
Foreign nationals/tourists: If you registered with a passport, you may be asked for passport copy, entry details, and video KYC if abroad.
Dual-SIM phones: Block both if you lost the phone and both numbers are yours; separately request IMEI blacklist for the device.
Found later: You can ask to lift a temporary suspension after re-verification. If it’s already permanently deactivated, you’ll need replacement provisioning.
Roaming abroad: Use the carrier’s international hotline, app/web chat, or email channel. Some PTEs allow video-KYC and will courier a replacement eSIM or activate via QR.

6) Evidence and documents (keep these handy)

Subscriber details: Number, full name, address, birthday, registered ID type/number.
Proof of identity: At least one primary government ID (two is better).
Proof of line use: Last top-up date/amount, last bill (postpaid), SIM serial if you have the pack, or device IMEI.
Affidavit of Loss (if asked; template below).
Police blotter (if there’s fraud or you need bank/e-wallet support).
SPA/Board Resolution (if acting for someone else/corporate).

7) Affidavit of Loss (short template)

Affidavit of Loss – SIM Card I, [Name], of legal age, [citizenship], with address [Address], after being duly sworn, state:

I am the registered subscriber of mobile number [+63…] under [Carrier];

On [date/time] at [place], my SIM card was lost/stolen and is beyond my control;

I request the immediate blocking/suspension of said number and will apply for replacement;

This affidavit is executed to attest to the loss for all legal intents. [Signature / ID details] (Jurat/Notary block)

8) Model request to carrier (chat/email/app note)

Subject: URGENT – Lost SIM Block & Replacement Hi [Carrier], I’m [Full Name], the registered owner of [+63…]. SIM lost on [date/time] at [place]. Please immediately block/suspend all services and flag my SIM registration. I will proceed with replacement (same number). ID: [Type/No.] | DOB: [mm/dd/yyyy] | Last load/bill: [details]. Kindly confirm with a ticket number and advise required steps/documents. [Name] / alt contact: email & backup phone]

9) Device blocking vs SIM blocking (don’t confuse these)

SIM block stops use of your mobile number; it protects OTPs and incoming calls/SMS.
IMEI blacklist stops your device hardware from registering on networks. Do both if the phone itself is missing.
Content on the phone (photos, apps) is not erased by network blocks—use device “erase/lock” features via Apple/Google and change cloud passwords.

10) Data privacy & retention

Your submitted IDs/biometrics for SIM registration and any re-KYC are sensitive personal data. Carriers must:
- Collect/process only what’s necessary,
- Keep it secure, restrict access on a need-to-know basis,
- Retain only for periods allowed by law/regulation/policies, then dispose securely,
- Disclose only to law enforcement with due process or where legally required.

If you suspect misuse of your registration data, you may complain with the carrier, NTC, and the NPC (privacy regulator).

11) Timelines & fees (what to expect)

Blocking/suspension: typically immediate once identity is verified.
Replacement/SIM swap: same day to a few business days, depending on verification and store visit / eSIM. Reasonable fees may apply (often waived for postpaid under plan rules).
IMEI blacklist: can take hours to a couple of days to propagate across networks.

12) Common pitfalls & how to avoid them

Delay in reporting → attacker intercepts OTP and empties e-wallets. Act fast.
Talking to impostor channels → only use official hotlines/apps/stores; ignore links in SMS.
Handing out OTPs → carriers/banks never ask for your OTP or MPIN.
Inadequate verification info → keep a secure note of SIM serial, account numbers, and recent load/bill to pass KYC quickly.
Assuming SIM block = account security → also change passwords, move 2FA to authenticator apps, and update numbers on file.

13) What if the carrier refuses to block or replace?

Escalate within the carrier (supervisor/complaints unit).
File a written complaint with NTC (attach IDs, ticket logs, affidavit, any losses).
For financial loss (e-wallet/bank), use the BSP Consumer Assistance Mechanism in parallel and submit the police blotter.
Consider civil action for damages if negligence is clear (e.g., wrongful SIM swap, failure to follow KYC/IRR).

14) FAQs

Q: Can someone re-register my lost SIM under their name? A: They shouldn’t be able to if you’re already registered; the identity match will fail. Blocking and registry flagging adds protection.

Q: I’m on postpaid—do I still need to “register”? A: Postpaid lines are deemed registered via your subscriber contract, but you must still verify identity for a block/swap.

Q: Will I lose my number if I can’t visit a store? A: Not necessarily. Ask for video-KYC or authorized representative with SPA and IDs. eSIM can often be provisioned remotely.

Q: Can I just keep the line suspended indefinitely? A: Carriers may auto-deactivate after a defined dormancy period. If you want to retain the number, proceed with replacement.

Q: My number was used for scams after loss—am I liable? A: Criminal liability targets the user who committed the offense. But act promptly to block, file a blotter, and document timelines to protect yourself and support investigations.

15) Quick checklist (printable)

✅ Change passwords; migrate 2FA from SMS to app
✅ Call/app-chat carrier → block/suspend + registry flag (get ticket #)
✅ Request SIM/eSIM replacement (same number)
✅ File police blotter if fraud risk; prepare affidavit if needed
✅ IMEI blacklist for missing phone
✅ Alert GCash/Maya/banks to freeze/secure
✅ Update number in government/critical services
✅ Keep copies of tickets, dates, and times

Bottom line

Under the SIM Registration Act, you control your registered number: you can block it immediately when lost, replace it after re-KYC, and demand privacy-compliant handling of your data. Move fast, use official channels, and pair the SIM block with account hardening and IMEI blacklisting (if the device is gone). If a carrier drops the ball, escalate to NTC and preserve your paper trail.