I have signal bars but no internet.

Bars can belong to the home SIM. Open the cellular settings and confirm mobile data is assigned to the Vietnam line, with roaming off on that line.

I have no bars at all.

Confirm airplane mode is off and the Vietnam line is turned on. You need to be in Vietnam. A local profile will not attach properly abroad, and that attach is what starts the plan.

It worked this morning and died tonight.

Check whether you used the 5GB. There is no slow speed after the cap. Service returns at 23:59 GMT+7.

Should I toggle roaming on just to test?

No. Roaming on is the wrong mode for this product and can confuse the registration.

When do I contact support?

After the checklist, with a screenshot of the data-line screen, the phone model, and the order email. If the QR never installed, say so. Replacement is for a defective, never-activated QR.

No data after landing in Vietnam

Set mobile data to the Vietnam line, turn mobile data on, and set data roaming off. Wait five to ten minutes. If the day’s 5GB is already used, data stays off until 23:59 Vietnam time. Do not delete the eSIM.

Ten minutes of checks, in order

Airplane mode off. You are physically in Vietnam, not still on the jet bridge with the radio forced off.
The Vietnam line is enabled. The label might be the one you typed, or a carrier name that appeared after install.
Mobile data is on, and the selected mobile-data SIM is the Vietnam line, not your home line.
Data roaming for the Vietnam line is off.
Wait five to ten minutes. Walk out of the concrete arrivals hall if you are still inside it. A crowd of phones registering at once is a bad sample.
Toggle airplane mode once, not twenty times. Then wait again.

The failure that is actually the plan working

This plan gives 5GB of high-speed data and then stops. It does not drop to 128 kbps. It does not keep WhatsApp alive. If you hotspot a laptop on the bus from the airport, you can arrive at the hotel with an empty day. The reset is 23:59 Vietnam Standard Time. Buying a second plan is possible. Topping up this same profile is not, today. The phone’s own data counter, reset when you landed, is the honest remaining-data tool. We do not ship a separate usage app.

APN only after the line settings are right

The installed profile normally writes the APN itself. The public Viettel internet APN is v-internet, with username and password left blank. Change it only if mobile data is definitely on the right line and pages still fail. The APN page has the iPhone and Android paths. A wrong APN looks like zero data with full bars. A correct APN will not fix a line that is still pointed at your home SIM.

Dual-SIM phones love to be helpful. iPhones may switch cellular data to the other line if you allow it. Androids may keep “smart” data switching on. Turn those helpers off while you test, or you will fix the Vietnam line and then watch the phone spend data on the home SIM, which is how a roaming bill happens. Bank SMS is a separate problem and wants the home line powered on for messages only. That guide is linked below the fold in related pages.

If nothing in this list works, stop. Screenshot Settings where the data SIM and roaming switch are visible, and email contact@esimforvietnam.com or Telegram @AIdePaul. Say whether the QR ever installed. Do not remove the eSIM to “start clean.”

No data after you land in Vietnam

Ten minutes of checks, in order

The failure that is actually the plan working

APN only after the line settings are right

Get the local Viettel eSIM

Questions