How it works
How does a travel eSIM work? Step by step
A travel eSIM is bought online, installed in 1 minute before you fly, and connects by itself to the NTT docomo network when you land in Japan. Then you track your data and top up in the app. Your UK SIM stays in your phone.
In short
An eSIM is a SIM built into your phone
It does the job of a SIM card, without the card: it’s built into your phone, and your plan downloads to it. With Mobile Companion, it gives you data in Japan, alongside your UK SIM.
For the full definition, read what an eSIM actually is. Here, we show you how it works in practice, from buying your plan to getting online in Japan.
| Step | When | Where |
|---|---|---|
| Check your phone | Before you buy | In your settings, or in the app |
| Buy your plan | Before you leave | On the website or in the app |
| Install your eSIM | Before you leave, on Wi-Fi | On your phone |
| Get connected | When you land in Japan | On your phone: turn off aeroplane mode |
| Track your data and top up | During your trip | In the app, or your account on the website |
Words worth knowing
- Installation QR code: the code you get after you buy. You scan it to install your eSIM.
- Data line: a line that gives you the internet but no phone number, like your Mobile Companion eSIM.
- Top-up: extra data you add to your plan during your trip.
Before you buy
Before you buy: check your phone
First things first: a phone that supports eSIM and is unlocked.
That covers iPhones since the iPhone XS and iPhone XR, Google Pixel phones since the Pixel 3a and most recent Samsung Galaxy models. To be sure, search for “eSIM” in your settings, or dial *#06#: if an EID number appears, you’re good to go.
Find your exact model on our page about an eSIM-compatible phone. And if your phone came from a network, on contract for example, check that it’s unlocked: otherwise, it will refuse the eSIM.
Step 1
Step 1: choose and buy your plan
Pick a plan, pay, and that’s it.
Choose your plan by how much data you need and how long you’re staying, on the website or in the app: it’s the same account. You pay online, and your QR code arrives straight away.
No need to wait until the day before you fly: your plan starts when you first connect in Japan, not when you buy it. Prices are in euros: your bank converts the amount into pounds when you pay, and may charge a fee for it.
Step 2
Step 2: install your eSIM with the QR code
At home, on Wi-Fi: installing takes 1 minute.
Connect to Wi-Fi
You need an internet connection to download the eSIM. Do it at home, when you have a quiet moment.
Start the installation
From the app, or by scanning your QR code shown on another screen, such as a computer.
Leave it until Japan
Your eSIM is ready, and your UK SIM stays where it is. There’s nothing more to do before you land.
On iPhone
Start from the Mobile Companion app or scan your QR code, then follow the steps on screen. Your eSIM appears as a second line, next to your UK SIM. Every screen is in our iPhone set-up guide.
On Android
Same idea: start from the app, or scan your QR code from your SIM settings (on Samsung, Settings > Connections > SIM manager). Every screen is in our Android set-up guide.
Why before you leave? Because when you land, you won’t necessarily have Wi-Fi to hand.
Step 3
Step 3: switch it on when you land in Japan
When you land, turn off aeroplane mode: your eSIM connects to the NTT docomo network by itself. No counter, no queue, no settings.
- The NTT docomo networkOne of Japan’s major mobile networks, in 5G where it’s available.
- A Japanese IP addressIt’s a real Japanese line: websites and apps see you as a local connection.
- Your plan startsYour validity begins with this first connection, not before.
Your UK SIM stays in place for your number. The eSIM takes care of data: maps, messages, social media. Not sure when to do each step? Here’s the right time to activate your eSIM.
Step 4
Step 4: track your data and top up in the app
During your trip, the Mobile Companion app keeps an eye on your plan.
Your eSIM list shows your eSIM and its status, and you can follow how much data you’ve used. Running low? Choose a top-up and pay in the app, or from your account on the website.
Every feature of the app is here: top up your data in the app.
Hotspot
Sharing your data (hotspot)
Hotspot and tethering are allowed with your Mobile Companion eSIM.
Turn on the hotspot in your phone’s settings (Personal Hotspot on iPhone), then connect your laptop, a tablet or a friend’s phone. Everything you share uses your plan’s data, so allow a little more if other devices connect.
On your phone
What stays the same: your UK number
The eSIM is added to your phone. It doesn’t replace anything.
- Your UK SIM stays putYour number doesn’t change: calls and texts still go through your UK SIM.
- WhatsApp keeps your accountYour account stays linked to your usual number. Your chats carry on, using the eSIM’s data.
- The eSIM handles dataIt gives you the internet in Japan, but no phone number.
Keep your UK SIM switched on for calls and texts, but turn off data roaming on it so it doesn’t use data abroad. What your UK network charges for calls and texts in Japan depends on your plan: check before you go.
FAQ
Your questions about how it works
How do I get an eSIM?
Buy a plan on the website or in the app, then install the eSIM on your compatible phone, from the app or with the QR code you receive straight away.
Can I install it before I travel?
Yes, and that’s the best way: install it at home on Wi-Fi. Your plan only starts when you first connect in Japan.
Do I need the internet to install the eSIM?
Yes, you need a connection to download it. Install it at home, on Wi-Fi, before you leave.
How do I activate it in Japan?
When you land, turn off aeroplane mode: your eSIM connects to the NTT docomo network by itself. There’s no setting to switch on.
Are eSIMs reliable?
An eSIM uses the same mobile network as a regular SIM card: here, NTT docomo’s. Only the format changes, since it’s built into your phone.
Do I keep my UK SIM?
Yes, the two work side by side: the eSIM for data in Japan, your UK SIM for your number, calls and texts.
How does an eSIM work on iPhone?
You install it from the app or with your QR code, and it’s added as a second line, next to your UK SIM. iPhones have had eSIM since the iPhone XS and iPhone XR.
Can I use my eSIM as a hotspot?
Yes, hotspot and tethering are allowed. Shared devices use your plan’s data, so allow a little more.
What happens when my data runs out?
You top up from the app or your account on the website. As you can follow your usage in the app, you’ll see it coming.
What if I need help?
Message support on WhatsApp, 24/7, in English or French, or email contact@mobile-companion.com.
More answers are in the help centre, and you can contact the support team at any time.
Ready to go?
Online as soon as you land
Your eSIM on NTT docomo’s 5G network, installed in 1 minute before you fly. From €1.20.
See the plans