Travel eSIM Configuration

Summary:

With the introduction of eSIM—a digital SIM card embedded directly into a device's hardware, replacing the need for a physical, removable card— traveling abroad and staying connected has never been easier.

If you are a T-Mobile customer, you have everything necessary for seamless connectivity. However, if your home carrier is not T-Mobile, utilizing a travel eSIM can be extremely beneficial.

First, check that your mobile phone is unlocked and of an eSIM-compatible model, then you may install an eSIM for travel. If you received your iPhone via your home carrier's plan, it is likely your phone is locked to only work with your home carrier's cell frequency. To see if your iPhone is locked, do Settings -> General -> About, and scroll down to see the "Carrier Lock" field. If it is unlocked, it should say "No SIM restrictions." Otherwise, you may call your carrier to ask them to unlock your phone. They might deny your request because you need to have owned the phone for at least six months. Alternatively, they could unlock it remotely, or they might require you to pay off your phone's remaining balance first.

There are many eSIM vendors who promote their product through YouTube influencers. The prices are very competitive, so one has to look for support and features. For us, the support for iMessage is a crucial feature.

You may purchase an eSIM for a specific country or for a region. The installation process may be a little bit different from brand to brand, but the configurations after installation are the same.

Vincent and I just returned from a 19-day trip to Japan. I bought a 30-day, 5 GB data plan from Nomad for USD $11, while Vincent opted for a similar plan from Japan Wireless, which cost about USD $10. We deliberately purchased from two different brands to see if one would work better than the other. Both plans worked very well during our trip, including receiving and sending iMessages. We called each other using WhatsApp if we got separated in a crowded place. You may choose to call using Line, Facetime or any other voice-over-internet-protocol app.

Here is an excellent article from Nomad on HOW-TO use iMessage with a travel eSIM. https://www.getnomad.app/blog/how-to-use-imessage-with-travel-esim

In Summary,

Can I use iMessage with a data-only eSIM?
Yes, iMessage works perfectly with data-only eSIMs such as Nomad's travel eSIMs. Since iMessage operates entirely over the internet, it only requires a data connection—not SMS or voice capabilities.
Verify iMessage Settings
First, let's verify your current configuration:
  1. On your iPhone, go to Settings > Apps > Messages
  2. Check that the iMessage toggle is switched ON (green)
  3. Tap Send & Receive to see which numbers and email addresses are configured for iMessage
  4. Under "You can receive iMessages to and reply from’, ensure your primary phone number is selected.
  5. Under "Start new conversations from”, select your primary phone number.
Disable 'Send as SMS'
To avoid unexpected charges:
  1. Go to Settings > Apps > Messages.
  2. Toggle OFF Send as SMS (or "Send as Text Message" in newer versions of iOS ) to send as SMS. (Note: SMS messages are in green bubbles.)

Installation:

  • Register: Every vendor wants you to register with an ID/pwd. Do that on a desktop computer, because it is easier to do so from a larger screen. I would recommend the California-based Nomad brand at https://www.getnomad.app/. It is advantageous to establish an account with a vendor that sells eSIMs for many countries, because the next time when you need to buy another eSIM, you'll already have had an account established with this vendor and also have had its app installed on your iPhone.
     
  • Download the vendor's app on your mobile device: Go to the vendor's home page and tap the Download App link. Install its app on your iPhone. (You'll need to know your Apple ID and password to install an app.)
    - Log in to the mobile app with the ID/pwd you created from your desktop computer.
    - Select what plan you want to purchase and pay for it online. There is no need to buy an unlimited data plan unless you want to stream videos while out and about. For a 19-day trip, I only used 3.34 GB of data, therefore, a 5 GB data plan was good enough for me. Besides, on the app, there is a button to tap to buy more data should you need it.
    - You'll be guided through the installation of this travel eSIM. The default name for this travel eSIM is "Secondary" (assuming you only have a Primary eSIM from your home carrier), but you can relabel it to any other name you like.
    - Activate the travel eSIM too. It will be turning and turning for a few minutes trying to find a designated cellular provider in your destination country to connect to, but it cannot find any because you are still at home. A few minutes later, the turning will stop. For the majority of the vendors, your number of days does not start counting until you are at your destination country and connected to a designated cellular provider.
     

Configurations:

1) Before leaving home:
    a. Make sure your home carrier's eSIM (the Primary eSIM) is toggled OFF for Data Roaming.
    b. Make sure the travel eSIM is toggled ON for Data Roaming.
    c. Turn the travel eSIM OFF for now.
    d. Configure to use your USA phone number for voice and Facetime.
    e. Verify your iMeesage is set to Send & Receive from your USA phone number.

In Settings > Cellular > Cellular Data > select to use your Primary eSIM.
In Settings > Cellular, set the Default Voice Line to use your Primary eSIM, which means using your USA phone number.
From the same screen, tap the Secondary eSIM to label it another name, here I named it "Nomad for Japan" and choose to turn it off for now.
Perform the 5 steps in "Verify your iMessage Settings" in the Summary section to verify your iMessage is Send & Recieve from your USA phone number.

In Settings > Cellular > Primary, verify that the Data Roaming is OFF (not in green) for your Primary eSIM. It should remain OFF all the time.

2) After you have arrived at your destination
    a. Turn OFF Airplane mode.
    b. Turn on your travel eSIM, and make sure its Data Roaming is ON.
    c. Configure to use this travel eSIM for Cellular Data, and disallow Cellular Data Switching.
    d. Double check that your iMeesage is set to Send & Receive from your USA phone number.

In Settings > Cellular > tap the name of your travel eSIM to Turn ON This Line. 
In Settings > Cellular > tap the name of your travel eSIM again to set its Data Roaming to ON.
 

In Settings > Cellular > Cellular Data, select to use your travel eSIM for data, and DO NOT ALLOW for Cellular Data Switching. This way, your data usage will only come from your travel eSIM, and not your Primary.

At this point, in Settings > Cellular, you should have the screen similar to the above. Your Cellular Data is configured to use your travel eSIM, and you have both eSIMs ON.

Double check the 5 steps in "Verify your iMessage Settings" in the Summary section to make sure you will send and receive iMessages from your US phone number.

Perform disabling of "Send as Text Message" to disable sending as SMS (the green bubbles) as described in the Summary section.

iMessages (the blue bubbles) are free when you are connect to the internet.


From the vendor's app screen, you may tap "Manage" to see how much data you have remaining at any point in time, or to buy more data. At the end of the trip, I still have 1.66 GB of data left on my travel eSIM.

After you have returned to the USA

Configure your settings to be the same as before you leave home. i.e., turn OFF the travel eSIM, and set your Cellular Data to use your Primary eSIM.

While at home, you may also want to enable the "Send as Text Messsage" in sending in SMS green bubbles when iMessage is unavailable.

You may delete your travel eSIM when you no longer need it.