To turn off data switching on iPhone, open Settings > Cellular > Cellular Data, select the travel eSIM and disable Allow Cellular Data Switching.
This keeps the selected travel eSIM as the designated data line and reduces unintended primary-SIM data use. Mobile data during a call on the other line may behave differently after the change.
NoveSIM travel eSIMs are data-only, so the primary SIM can remain the voice line while NoveSIM handles data.
Quick answer: Go to Settings > Cellular > Cellular Data, choose the travel eSIM and turn off Allow Cellular Data Switching. Keep Data Roaming off on the primary SIM and enable it on the travel eSIM when its instructions require it.
Configure this setting after selecting a plan that covers the whole itinerary. The NoveSIM destination list lets you open the relevant country or regional option and verify its allowance and validity before assigning it as the iPhone’s data line.
Turn Off Cellular Data Switching in 5 Steps
- Open Settings.
- Tap Cellular or Mobile Data.
- Tap Cellular Data.
- Select the travel eSIM.
- Turn off Allow Cellular Data Switching.
Why This Helps Abroad
It reduces the chance that iPhone will use the primary line for data when the travel line is weak or while the other line is involved in a call. It does not block ordinary calls, voicemail or SMS charges on the primary carrier.
For the complete two-line setup, read how to keep your number with eSIM data.
Check Both Roaming Controls
Open each line separately. Enable Data Roaming on the travel eSIM when its instructions require it, and keep it off on the primary SIM if preventing home-carrier data charges is the goal. The Data Roaming guide explains why the two lines need different settings.
What Changes during Calls?
Apple notes that an iPhone uses one mobile-data network at a time. With switching off, mobile data may be unavailable during a call placed on a line that is not the designated data line, depending on carrier and Wi-Fi Calling support. This is a trade-off, not evidence that the eSIM has failed.
Verify the Result
- Turn off Wi-Fi.
- Open Control Centre and confirm the intended data carrier.
- Load a website.
- Check cellular usage later to confirm the primary line did not consume data.
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FAQ
Should Allow Cellular Data Switching be off for travel?
Usually yes when you want the travel eSIM to be the only data line.
Will turning it off disable my primary number?
No. The line can remain active for calls and SMS.
Can calls interrupt travel-eSIM data?
They can under some dual-SIM and carrier conditions when switching is disabled.
Does this stop every roaming charge?
No. Calls, SMS and voicemail on the primary carrier can still be chargeable.
Final Recommendation
Select the travel eSIM first, then disable Allow Cellular Data Switching.
Configure roaming separately on both lines and verify usage with Wi-Fi off.
This produces predictable data routing while preserving the primary number when needed.
