How to turn on data roaming for an eSIM
Data Roaming is the switch that lets a travel eSIM use a partner network abroad. On iPhone: Settings → Cellular → your GlobalSIM line → Data Roaming on. On Samsung: Settings → Connections → Mobile Networks → Data Roaming on. Turn it on when you arrive and keep the eSIM as the line for Mobile Data.
Does the roaming switch cost extra?
No. It only opens the partner network to the line; the data you use comes out of the package you already bought.
Roaming is on but there is still no internet. What now?
Check that Mobile Data points to the eSIM, restart the phone, or toggle Airplane mode on and off once. If the network still does not attach, select the operator manually.
Should I turn roaming on for my Mongolian SIM too?
No — leave the Mongolian line off or without roaming and give the data to the eSIM. That way your home number is never billed for roaming.