You've landed, your eSIM is installed, everything looked good during setup. But your phone is still chewing through your home carrier's data — or worse, racking up roaming charges — because it's ignoring the eSIM entirely. The profile is there, it shows in settings, it even shows a signal. Your apps just refuse to use it.
This is a dual-SIM priority problem, and it's one of the most frequent issues travelers run into after getting an eSIM set up correctly. The fix isn't complicated, but the exact steps depend on your phone model and OS version, and the terminology varies enough between devices that it's easy to miss the right setting.
Understanding the Problem: Dual SIM and Data Priority
Modern phones support running two SIMs simultaneously — one physical, one eSIM, or two eSIMs on some models. Each SIM can have its own number and network connection. But only one SIM handles mobile data at a time, and your phone has a setting that determines which one.
When you install a new eSIM, most phones don't automatically switch data to it. They leave data on whatever was previously set as the default — usually your physical SIM with your home number. This means you could be fully connected to a local network through your eSIM without ever using a byte of it, because the phone is routing everything through the physical SIM instead.
The solution is to explicitly set your eSIM as the data SIM. That's the core fix. The steps below walk through how to do it on each major platform, plus what to do if it still doesn't work after changing the setting.
Fixing Data Priority on iPhone
iPhone handles dual-SIM configuration through the Cellular settings, and there are a few specific toggles you need to set correctly.
Step 1: Set the eSIM as your cellular data line
- Go to Settings → Cellular
- Tap "Cellular Data" near the top (this shows which line is currently used for data)
- Select your eSIM plan from the list
This is the primary fix. Once you select the eSIM as the cellular data line, your phone will route mobile data through it rather than the physical SIM.
Step 2: Enable "Allow Cellular Data Switching" if needed
Below the "Cellular Data" option, you may see an "Allow Cellular Data Switching" toggle. This allows iOS to automatically switch to the other SIM for data if the primary one has no signal. For travelers, this setting can accidentally route data back to your home SIM in areas where the eSIM has weaker coverage. Consider turning it off if you want strict control over which SIM is used.
Step 3: Enable Data Roaming on the eSIM line
Go back to Settings → Cellular and tap on your eSIM plan name. Make sure "Data Roaming" is enabled. Without this, the eSIM will register on the network but won't transmit data — it looks like a signal problem but it's actually a roaming permission issue.
On iPhone, after switching the cellular data line, it can take 30–60 seconds for data to start flowing through the new SIM. Be patient before assuming the fix didn't work. You can confirm which line is active by pulling down the Control Center — the carrier name shown is the one handling data.
Fixing Data Priority on Android
Android fragmentation means the settings path varies by manufacturer. Here are the steps for the most common brands.
Samsung Galaxy
- Go to Settings → Connections → SIM card manager
- Tap "Mobile data"
- Select your eSIM as the mobile data SIM
- If prompted, confirm you want to switch
Also check: Settings → Connections → Mobile networks → Data roaming → ensure roaming is enabled for the eSIM. Samsung sometimes has roaming settings that are separate per SIM.
Google Pixel
- Go to Settings → Network & internet → SIMs
- Tap the Preferred SIM section or look for a "Mobile data" assignment
- Select your eSIM
On some Pixel Android versions, you may see a "Use SIM" toggle per SIM entry. Make sure the eSIM toggle is on and that it's set as the preferred data SIM.
Other Android phones
The general path: Settings → Network/Connections → SIM cards or Dual SIM → look for "Preferred data SIM" or "Mobile data" and select the eSIM. If you can't find it, use the settings search bar and type "mobile data" or "SIM" — it usually surfaces the right screen.
Data Still Not Working After Setting the eSIM as Primary
You've set the eSIM as the data line, roaming is on, and data still isn't working. Here's what to check next.
The eSIM line isn't enabled
Separate from data priority, each SIM line needs to be individually turned on. On iPhone: Settings → Cellular → tap the eSIM → make sure "Turn On This Line" is active. On Android: SIM card manager → tap the eSIM → confirm it's enabled. A line can be registered and show a carrier name while technically being toggled off, which blocks it from sending or receiving data.
APN settings aren't configured
If the line is enabled and set as the data SIM but still not connecting, the APN (Access Point Name) might be blank or incorrect. This is more common on Android than iPhone. Check: Settings → Connections → Mobile networks → Access point names → look for an entry for your eSIM. If it's blank or missing, you'll need to enter the APN details your eSIM provider specifies.
There's a conflict with a VPN or firewall app
VPN apps, firewall apps, or content blockers can sometimes prevent data from flowing after a SIM switch, particularly on Android. If you have any of these active, temporarily disable them and test connectivity. This is an easy thing to overlook but a genuine cause of data not flowing even when everything else looks right.
The phone needs a restart
After changing the data SIM and enabling roaming, a full restart forces the phone to re-register on the network with the new settings applied. This clears any cached SIM state that might be causing the phone to still try routing through the old SIM. It takes less than a minute and resolves a surprising number of persistent issues.
A Common Mistake: Expecting Data to Switch Automatically While Abroad
Some travelers install a travel eSIM, land in their destination, and wait for their phone to just start using it. That rarely happens without manual configuration. Phones don't automatically detect "oh, this eSIM is cheaper here" and switch — they use whichever SIM was set as default before you left.
This is one of the setup mistakes worth preventing before your trip, not discovering at the airport. Our article on common eSIM setup mistakes covers this and several other configuration issues that are easy to head off with a quick check before boarding.
Keeping Your Home Number Active While Using eSIM Data
Many travelers want the best of both: eSIM data from a local plan, while keeping their home number active for calls, WhatsApp, and OTPs. This is absolutely possible and the right way to handle it.
Set your eSIM as the data SIM (as described above), and keep your physical SIM active for calls and texts. On iPhone, you can separately set the default voice line under Settings → Cellular → Default Voice Line. On Android, look for "Calls" or "Voice calls" assignment in the SIM manager, separate from the data SIM setting.
With this configuration, your apps use the eSIM's data connection, but incoming calls and SMS on your home number still ring through. Your banking apps and any OTPs sent to your home number will arrive normally because that SIM is still active — it's just not being used for data.
If you disable your physical SIM entirely to save battery or avoid accidental roaming charges, calls and SMS to your home number won't come through. Only disable the physical SIM if you're certain you don't need it for voice or verification codes during the trip.
Testing That the eSIM Is Actually Being Used
After making the changes, confirm that data is genuinely flowing through the eSIM. The quickest check: on iPhone, open Control Center — the carrier name in the top left should match your eSIM provider, not your home carrier. On Android, pull down the notification shade and check the network indicator.
A more definitive test: temporarily disable Wi-Fi and open a browser or app. If data loads, the eSIM is working. If it doesn't, go back through the steps above — it usually comes down to either roaming not being enabled or the data SIM assignment not having saved properly.
If you're still having trouble after working through all of this, the issue may be signal-related rather than configuration-related. Our eSIM no signal guide covers the next set of diagnostic steps for when the line appears to be set up correctly but still isn't getting through. And if you want to browse plans for your next destination once this is sorted, you can compare eSIM plans by country.