The iMessage SIM Lock Trick I Use When Traveling With eSIMs

One of the biggest annoyances when traveling internationally is avoiding excess mobile data charges — especially if you want to keep using your regular phone number for iMessage and FaceTime during your travels.

Over the past few years, I've used a simple workaround that lets me:

• Turn off my home carrier SIM
• Use a foreign eSIM for data
• Keep iMessage and FaceTime working with my regular phone number

It's often referred to as the "iMessage SIM lock trick."

I use this on nearly any trip where I'm traveling abroad and use an eSIM to avoid the steep travel passport fees that providers like Verizon and AT&T charge.

Here's how it works.

Why This Trick Matters

When you install a travel eSIM (I personally use Ubigi), your phone can switch to that SIM for mobile data. The problem is that if you simply turn off your home SIM, iMessage will deregister your phone number.

That means your messages default to your Apple ID email instead of your phone number. As I've learned the hard way, that can cause confusion and missed texts.

This SIM lock trick keeps your iMessage associated with your at-home phone number while allowing you to use a foreign eSIM.

How the SIM Lock Trick Works

The key is setting a SIM PIN on your primary home line and leaving that SIM in a "locked" state after restarting your phone.

When the SIM is locked:

• It cannot connect to the cellular network
• It cannot incur roaming charges
• It cannot send or receive traditional SMS

You'll see a pop-up asking for this after restarting your phone, but the key is to ignore it.

But because the SIM is still physically present and associated with your device, your iPhone keeps your phone number active for iMessage and FaceTime.

Step-by-Step: How to Set It Up

1. Set a SIM PIN on Your Primary Line

On your iPhone:

• Go to Settings > Cellular (or Mobile Data)
• Select your primary SIM
• Tap SIM PIN
• Toggle it on

You'll need the default carrier PIN:

• Often 1111 for Verizon or AT&T
• Often 1234 for T-Mobile

Then change it to something you'll remember. Do not forget this number!

2. Install Your Travel eSIM

I use Ubigi, which allows you to install an eSIM once and load multiple country data packs. This works especially well for multi-stop trips.

Once installed, activate the appropriate country plan.

3. Restart Your iPhone

Power the phone off and back on.

When the phone restarts, it will prompt you to enter the SIM PIN for your primary line.

Tap Cancel in the upper left hand corner. This leaves the primary SIM in a locked state.

4. Configure Cellular Settings

• Go to Settings > Cellular
• Set your new eSIM as the primary line for Cellular Data
• Make sure Data Roaming is disabled for your home SIM

5. Confirm iMessage Settings

Go to Settings > Messages > Send & Receive and make sure:

• Your phone number is checked
• Your Apple ID email is also checked
• Your phone number is selected under "Start New Conversations From"

At this point, iMessage and FaceTime should continue working with your home number over your travel eSIM's data connection.

When you return home you'll follow these steps in the reverse order — removing the lock on your primary SIM, and toggling that back as your cellular data SIM.

Why I Use This With Ubigi

I often travel through multiple countries in a single trip — for example during my winter around-the-world trip. With Ubigi, the phone automatically switches data packs based on location:

• 3GB Japan
• 1GB Qatar
• 1GB Denmark

This SIM lock trick ensures my U.S. number stays active for iMessage the entire trip. Best of all, the price is significantly cheaper than using my domestic carrier's travel plan.

What About Voice Calls?

Most eSIMs are data-only, which means:

• No traditional voice service
• No SMS

You can still use:

• FaceTime Audio
• WhatsApp calls
• iMessage
• Signal
• Slack
• Teams

If you need a traditional U.S. number for voice, one workaround is signing up for Google Voice, which works entirely over data.

It's not identical to a full cellular plan, but for most travelers, it covers everything needed.

Things to Keep in Mind

• If you enter the SIM PIN at restart, your home SIM will reconnect and may trigger roaming.
• You'll need to restart and enter the PIN again when you return home.
• This works best with modern iPhones that support dual SIM and eSIM functionality.

The Bottom Line

This is one of those small travel hacks that makes international trips smoother.

Using a travel eSIM like Ubigi already saves money compared to daily roaming plans from AT&T or Verizon. The SIM lock trick adds another layer of benefit by keeping your iMessage active.

If you're traveling internationally soon then this is a trick worth taking note of.