How to keep your Vietnamese phone number when you leave Vietnam in 2026

A two-week trip home is usually fine. The risk starts when you leave for two months or more, the SIM sits in a drawer and nobody tops it up. Below is what is known for sure about the deadlines, what comes only from secondary sources, and what to do before your flight.

How long a number lives without top-ups

A prepaid Vietnamese number is shut down in steps: first outgoing service is blocked (khóa 1 chiều), then incoming too (khóa 2 chiều), then the number goes back into the operator's pool (thu hồi về kho số) and is sold again. Each operator sets its own deadlines, and the chain starts either when your account validity runs out or after a long stretch with no activity.

VinaPhone has given the clearest timeline. In December 2024 it explained to the press why a number one customer had used for 15 years was sold to someone else, and spelled out the procedure (VietTimes, 9 December 2024, in Vietnamese):

The same case shows how this plays out in dates. Outgoing service was cut on 19 August 2024, the line was fully blocked on 29 August, the recovery window closed on 12 October, and the number was released again on 19 November. Before each of the two blocks, the operator sent three SMS reminders to top up. VinaPhone's position was that the customer never responded and the number "không phát sinh sử dụng dịch vụ viễn thông", meaning no telecom services were used. Fifteen years of use and registration in his own name did not save it.

We found no official Viettel page with deadlines. Pages from Viettel Store, the group's retail chain, describe a 60-day rule for the Tomato plan: within that period the number needs at least one transaction, meaning a top-up, a paid outgoing call, a paid SMS, mobile data or an answered incoming call. Long-standing and higher-spending customers get 90, 120 or 180 days instead. With no transaction, outgoing service is blocked and you get 10 days to top up before a two-way block, and 15 days after that the number is taken back. On the Economy plan, account validity depends on how much you top up: once it expires, outgoing service is blocked, a two-way block follows 10 days later, and the number is taken back after another 30 days (Viettel Store, in Vietnamese). A Sforum guide from September 2026 repeats the same figures. The pages are old and the cycle depends on the plan, so plan around the shorter figure.

MobiFone does publish a hold period on its official site: after a two-way block the number is kept for 30 days (MobiFone, in Vietnamese). For the MobiQ plan it spells out the whole cycle: after 60 days with no top-up or paid use, outgoing service is blocked for 10 days, then comes a 30-day two-way block, and then the number goes back into the pool for other customers. A top-up during either phase lifts the block (MobiFone, in Vietnamese). Other plans may run on a different cycle, so check yours at a store before you leave.

How many days each top-up buys depends on your plan. The operator's app shows the date your account is valid until. On Viettel, *101# shows your balance.

Blocks for skipped verification are a separate issue

Since 2026 a number can also be cut off for reasons that have nothing to do with your balance. Under Circular 08, subscribers who had not completed data verification lost outgoing service on 15 June 2026: more than 5 million at Viettel and nearly 3 million at VinaPhone. After 60 days they are fully blocked, and 5 days later the contract is terminated (VnEconomy, 15 June 2026, in Vietnamese). A top-up won't help here; you need to verify. How foreigners do it is covered in our guide to SIM face checks and VNeID. If your operator has asked you to verify, do it before you leave, because you can't walk into a store from abroad.

What you lose along with the number

Losing the number means losing access to everything that uses it as a login or a channel for codes. For a foreigner in Vietnam that usually means four things.

Your bank. Under Circular 50/2024/TT-NHNN, in force since 1 January 2025, banks verify online-banking customers logging in for the first time or from another device with an SMS OTP or voice OTP sent to the registered number, or with a biometric match (Thị trường Tài chính Tiền tệ, in Vietnamese). Some banks confirm payments with a Smart OTP code in the app, as VPBank does, but the registered number still matters: Circular 50 lists it among the verification methods. We found no major bank with an online procedure for a foreigner to change the number. Foreigners without VNeID have to register bank biometrics in person, so updating your number will probably mean a branch visit too, which you can't do from abroad. Which banks open accounts for foreigners is covered in our guide to opening a bank account in Vietnam.

Zalo. A Zalo account is tied to your number. You can change the number in your account settings on the phone where you are already logged in, and the confirmation code goes to the new number. You can't do it from the web version or a computer. If the number is gone and Zalo is open on only one phone, don't log out until you've changed the number: without a code to the old number, getting back in is hard. Linking an email is worth doing too, but it doesn't replace the number.

Grab. You can change the number in your Grab profile and keep your ride history, preferences and GrabRewards points (Grab Vietnam). More on the app itself in our Grab guide for Vietnam.

VNeID. If you have a VNeID account, your phone number is on its application form and receives its confirmation codes, for example when you reset the password. How a foreigner changes that number in VNeID is not officially described.

So anything you can move to email, another number or an in-app code, move before you leave, while the Vietnamese number still works.

How to keep your number while you're away

You can keep a Vietnamese number for several months if transactions keep happening on it and the SIM stays in the same phone. Here is the order:

1. Check in the operator's app when your account expires, and top up with a buffer.
2. Turn on international roaming while you're still in Vietnam.
3. Decide how you'll top up from abroad, and test it before your flight.
4. For a long trip, ask about a 6- or 12-month package.
5. Leave the SIM in the phone it's in now.
6. Move your bank, Zalo and other services to a backup channel.

Roaming: turn it on before you fly

You need roaming for your Vietnamese SIM to receive calls and SMS codes abroad. On Viettel, dial *138*1# for calls, SMS and data or *138*1*2# for calls and SMS only, and *138*2# to turn it off. The one condition is that the number is active and not under a two-way block. Viettel Store recommends registering before you leave the country so there is time to fix anything that goes wrong (Viettel Store, in Vietnamese). Prices depend on the country, network and package, so check the operator's roaming table for what an incoming SMS costs where you're going. From abroad, Viettel support answers at +84982198198.

Incoming SMS are not on the list of transactions under the 60-day rule. An answered incoming call counts on Tomato, but you can't count on other people calling. So roaming alone doesn't keep the number alive; it only lets you receive codes.

Topping up from abroad

If you have a Vietnamese bank account, top up through the banking app, in the mobile top-up section (nạp tiền điện thoại). Eximbank, for example, lets you top up prepaid numbers on any network from online banking, with the money taken from your account (Eximbank). The My Viettel app lists international cards among its payment methods, but it doesn't say whether cards from foreign banks are accepted, and some users report foreign cards being rejected in operator apps. International top-up services also sell Viettel credit, but we haven't checked their fees. Whatever you choose, test it once before you fly, not on the day your account has already expired.

A long package

Viettel offers prepaid packages for 6 and 12 months, paid up front. The app shows the current list and prices. Whether such a package keeps the number valid for its whole term, or the 60-day rule still applies, the operator doesn't say publicly. Ask at a store before buying, and ask them to show you the account expiry date after activation.

Don't move the SIM to another phone

You can leave your Vietnamese SIM in an old phone and take your main one abroad with a different card. That works if the old phone is the one the SIM was already in. If you move the SIM to a different handset, or reissue it as an eSIM on another phone, Article 8 of Circular 08/2026/TT-BKHCN kicks in: outgoing service is cut within two hours until you redo the face check. How that works is covered in the section on SIMs and changing phones. Viettel lets you do it in its app (Tạp chí Kinh tế Tài chính, 30 July 2026, in Vietnamese), but that route isn't officially described for foreigners on a passport. A store is the safer option, and you can't get to one from another country. Only reissue an eSIM while you're in Vietnam and have time to get to a store.

A backup channel for your accounts

Even with every precaution, the number can still go: you forget to top up, the operator changes its rules, the phone gets lost. So before you leave, link an email to Zalo, check that your bank's Smart OTP works without SMS, and change the number wherever you can do it online. Then losing the number is a hassle, not a lockout from your own money.

What to do if your number has already been cut off

You can get a disconnected number back as long as it hasn't been sold again. What to do depends on the stage:

If the block is for skipped verification, a top-up won't help. Complete the verification and service comes back right away, without waiting for any deadline. Viettel's hotline is 18008098.

At VinaPhone, a number under a two-way block is restored at a store, and you can't get there from abroad. If you're already away and notice outgoing calls are blocked, top up immediately, while the number is still at the first stage.

Once the number is gone, start with your bank: go to a branch with your passport and the new number. Then change the number in Zalo and Grab if you can still get into those apps.

Common mistakes

• Assuming the number is yours forever because it's registered to your passport. Registration in your name doesn't protect against blocking for inactivity: VinaPhone sold a number its owner had used for 15 years.
• Topping up before you leave and then forgetting about it. Money on the account is not the same as validity: on Viettel's Tomato plan, per Viettel Store pages, what counts is a transaction within 60 days, not the balance.
• Moving the SIM to another phone while abroad. That triggers a new face check under Circular 08/2026, which a foreigner probably can't complete from another country.
• Ignoring operator SMS because they're in Vietnamese. VinaPhone sent six warnings before the number was blocked. Your phone's translator can handle them.
• Not testing your top-up method in advance. A foreign card may be rejected in the operator's app, and you don't want to find that out on the last day.

FAQ

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