What ST120K actually is
ST120K belongs to the family of short alphanumeric codes Vietnamese carriers use to label prepaid packages: a letter prefix for the package type, then a number that usually tracks the headline allowance or the price tier. Vietnamese subscribers see these codes on carrier apps, on scratch cards and in the plan catalogue on this site.
If you are a visitor, the code is not the thing you need. It is a domestic label, not a travel product, and it is not something you order from VietSIM. The catalogue entry exists so Vietnamese readers can compare plans accurately — codes are quoted exactly as they are sold, for example V90B, and the network, validity and activation details come from the plan's own product record rather than from any summary.
Why travellers searching ST120K should buy an eSIM instead
A prepaid Vietnam eSIM does the job a local plan code cannot do for a short trip: it is bought in advance, in USD, and it is tied to your phone rather than to a shop counter or a Vietnamese ID registration.
Here is the practical comparison for a visitor arriving in Hanoi, Da Nang or Ho Chi Minh City.
| Option | What you do | What it costs you in time | Best for |
|---|---|---|---|
| Vietnam eSIM bought before departure | Order online, scan a QR code, install at home | Nothing on arrival — the profile is already on the phone | Most travellers, any trip length |
| Local prepaid SIM at the airport | Queue, show passport, get the SIM registered | 15–45 minutes depending on the terminal and the hour | Long stays, people who need a local number |
| Local plan code such as ST120K | Requires a Vietnamese subscriber account or a carrier app | Not available to a short-stay visitor in practice | Vietnamese subscribers |
If you want the detail behind the airport counter option, the guides for Tan Son Nhat and Noi Bai cover prices and opening hours.
What to buy from VietSIM
The store sells the Vietnam eSIM in eighteen interface languages with USD checkout. Pick the plan by data volume and trip length, not by plan code — the codes you see in the catalogue are a different market entirely.
- Short trip, light use (maps, messaging, a few bookings): a small data plan is enough.
- One to two weeks, normal use: a mid-size plan with a daily allowance that matches how much you stream.
- Hotspot and heavier use: check the tethering rules before you buy, because a plan that is generous on the phone can behave differently when shared.
Buy the Vietnam eSIM here: Vietnam eSIM store. It is the one-click route from this page to the plan.
Two things worth reading before you choose: what "unlimited" really means on a Vietnam eSIM, and the price guide that explains what moves the number up or down.
Installation and activation, in order
- Buy the plan and check the email for the QR code.
- Install the eSIM profile while you still have home Wi-Fi — do not leave it until the airport.
- Keep your usual SIM active for calls and banking until you land.
- On arrival, turn the eSIM line on and give it a minute to register.
- If nothing connects, switch airplane mode on and off once, then check the APN.
The full walkthrough, including first-connection problems, is in the activation guide. If your phone is the question rather than the plan, the iPhone and Android compatibility pages cover dual-SIM behaviour and what to do about WhatsApp.
Plan codes, network names and what to ignore
Vietnam's three main networks are Viettel, VinaPhone and MobiFone, and the coverage story differs by region rather than by brand reputation. If you want the comparison, it is here: Viettel, VinaPhone or MobiFone.
What you should not do is read a code like ST120K as a promise about speed or coverage. Plan codes describe a package; the network, validity and activation behaviour come from the product record, and any page that turns a code into a coverage guarantee is guessing.
If you have already ordered and lost the email with your installation link, the help centre is the place to start — there is no public order lookup page, and per-order links arrive by email.
A short checklist before you fly
- Phone is eSIM-capable and carrier-unlocked
- Plan matches trip length and data habits
- eSIM installed at home, not at the gate
- QR code email saved or forwarded to yourself
- Home SIM kept active for calls and one-time passcodes
- Offline maps downloaded for the first city
That is the whole job. ST120K is a catalogue code for Vietnamese subscribers; your trip needs a Vietnam eSIM, bought once, installed once, and left alone.