Install while you still have Wi-Fi
iPhone XS, XR, and later models support eSIM, with regional exceptions, especially mainland China. Settings, Cellular, Add eSIM, Use QR Code. When iOS asks you to label the line, pick a custom label and type Vietnam. When it asks which line is for mobile data, you can leave data on your home SIM until you land, then switch. When it asks about the default voice line, keep home. iMessage and FaceTime can stay on the home number so your Apple ID identity does not move.
The switches that matter after landing
- Settings, Cellular, tap the Vietnam plan, turn on Turn On This Line.
- Back one screen, Mobile Data, choose Vietnam.
- Inside the Vietnam plan, Data Roaming off.
- Cellular Data Switching, or Allow Cellular Data Switching, off.
- Wait five to ten minutes. The status under the line should stop saying No Service.
iOS will sometimes show the Viettel name and sometimes only your label. Either is fine. What is not fine is a row of bars on the home line while Vietnam says No Service and you are already in the taxi. Give the radio the ten minutes, especially inside Noi Bai or Tan Son Nhat. If you still have no session, try the manual APN path: Settings, Cellular, Vietnam, Cellular Data Network. The APN field should be v-internet. Leave username and password empty. Do not invent a proxy.
Models that will never work
An iPhone X or earlier has no eSIM. A mainland China iPhone of many generations is dual nano-SIM and also has no eSIM, even when the same marketing name in the United States is eSIM-only. The compatible-phones page describes those cases. The proof on the device is *#06#. An EID means the hardware is there. No EID means stop and do not pay for a QR you cannot install. If you already paid and the phone cannot take the profile, write to support before you try random installs. The refund page explains replacement versus a final sale.
Hotspot on iPhone is Settings, Personal Hotspot, once the Vietnam line is the data line. It spends the same 5GB. If hotspot says it is on and the laptop has no route, the phone itself probably has no route either. Fix data first. Low Data Mode and a VPN left over from the flight are worth turning off during the test. Turn the VPN back on after pages load, if you want it.
If you installed the plan and then restored the iPhone from a backup, iOS sometimes keeps the label and loses the working profile. Look at whether the line still has signal controls or only a dead row. Do not delete it while you are unsure. A screenshot of Cellular, sent to contact@esimforvietnam.com, is enough for us to tell you whether the profile is still the original one. The plan length is still 7, 15, or 30 days from the first real Viettel attach, and the daily 5GB rule is unchanged by any of these menus.