From within the Settings app, tap Network & internet.
Choose the SIM you'd like to change roaming settings for.
This tutorial explains how to turn data roaming on or off. Additionally, within the Mobile Network settings, you can change your preferred network type, add and edit access point names, and manually select a network by toggling off the Automatically select network toggle off."
Scroll to and tap or slide the Data roaming switch to ON.
Turning Data roaming on allows you to connect to data services while roaming. Turn Data roaming off to keep from incurring significant charges.
Tap OK.
You've completed the steps!
