Will the Viettel eSIM receive the OTP?

No. It is data only. The code has to come to the number your bank already has, which is the home SIM.

Should data roaming be on for the home SIM?

Leave home-SIM data off so you do not roam data by accident. Inbound SMS while abroad can still depend on your carrier’s roaming service even when data roaming is off. That is your carrier’s policy, and it can be delayed or billed.

iPhone data switching?

Turn Allow Cellular Data Switching off if you want to be sure data stays on Viettel. SMS does not need that switch.

The code never arrives.

Use the bank’s app approval or email code if it offers one. Ask the bank whether inbound SMS abroad is blocked. We cannot inject an SMS into your home number.

Can I put the home SIM in another phone?

Only if that phone will be on and in range when the bank sends the text. A SIM in a bag does not receive anything useful.

Bank OTP SMS while using an eSIM

Leave the home SIM enabled for calls and SMS, and set mobile data to the Viettel eSIM. Bank texts go to the home number. Whether they arrive abroad depends on your home carrier, not on Viettel, because this eSIM has no SMS.

Two lines, two jobs

A dual-SIM phone can keep your home number and a Vietnam data line awake together. Give each line one job. Home SIM: voice and SMS, mobile data off. Viettel eSIM: mobile data on, data roaming off, no expectation of texts. iPhone: Settings, Cellular, Default Voice Line is home, Mobile Data is Vietnam. Android and Samsung: preferred SIM for calls and for texts is home, mobile data SIM is Vietnam. Pixel is the same idea under Network and internet, SIMs.

What we cannot promise about the text

Travelers often hear that “data roaming off means no roaming charges, and SMS still works.” The first half is the safe setting for data. The second half is up to the home carrier. Some carriers deliver inbound SMS abroad on the signaling channel and charge a small fee or nothing. Some block inbound SMS until you buy a day pass. Some deliver them late. Viettel is not in that path. The OTP never touches our eSIM. If your bank only knows how to text a number, test that path once before you need it for a hotel or a card payment. Send yourself a message from another phone, or trigger a low-stakes code, while you are still on airport Wi-Fi and can fall back to email.

Habits that avoid a roaming bill

Home SIM data off. Visual voicemail and iCloud backup must not be allowed to use cellular data on that line.
iPhone Allow Cellular Data Switching off during the trip if you have been burned before.
Android “auto switch data SIM” off.
Prefer the bank’s app prompt over SMS when the app offers it. The app can use the Viettel data line.
Wi-Fi calling, if your home carrier supports it and you trust the Wi-Fi, is sometimes how inbound texts arrive. Turn it on only if you know your carrier’s rules. We do not enable it for you.

Grab, Maps, and chat do not need the home number. They need the data line. A card terminal that sends an OTP is the moment the home SIM earns its place in the phone. Keep it in the phone, powered, and selected for SMS. Removing it to “save battery” is how people miss the code and then blame the eSIM. Battery settings can restrict the home line too. Exempt the messages app from extreme battery saving on Android if texts arrive only when you open the app.

None of this changes the data plan. You still have 5GB high-speed per day on Viettel, hotspot included, reset at 23:59 Vietnam time, and no local phone number. If a service insists on a Vietnamese mobile number for registration, this eSIM will not satisfy it. That is a product limit, not a dual-SIM setting you missed.

Receiving bank OTP SMS while the eSIM has the data

Two lines, two jobs

What we cannot promise about the text

Habits that avoid a roaming bill

Get the local Viettel eSIM

Questions