TL;DR: Turn Data Roaming On for the RoameSIM line, set that line as Mobile Data, keep home-SIM roaming Off, then toggle airplane mode.
iPhone
Settings → Cellular → tap RoameSIM → Data Roaming → On. Settings → Cellular → Cellular Data → RoameSIM.
Android / Samsung
Settings → SIMs → eSIM → Roaming On. Set Mobile data preferred SIM to eSIM.
Dual-SIM traps
- Calls on home SIM, data on travel eSIM - correct setup.
- Data still on home SIM with roaming On - expensive and broken for travel data.
If roaming toggle is missing or greyed out
Carrier restrictions, MDM/work profiles, or an incomplete install can hide the toggle. Re-check install: unable to activate.
Next steps
No internet checklist · Connected but no data · 12 fixes
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Frequently Asked Questions
Why must travel eSIMs use data roaming?
They authenticate on visited partner networks. Without roaming, the line may show No Service or no data.
I enabled roaming but still no data - why?
You may have enabled it on the home SIM. Open the eSIM line specifically and set Mobile Data to that line.
Will roaming on my home SIM cause charges?
Yes. Keep home-SIM roaming Off and use RoameSIM for data.
Is roaming the same as airplane mode off?
No. Airplane mode disables radios; roaming is a per-line setting after cellular is on.