If there is only one line on the device: 

Go to Settings → Cellular → Toggle Cellular Data on or off to turn the line on or off.

If there are multiple lines on the device: 

Go to Settings → Cellular → Tap Cellular Plans and toggle Turn On This Line at the top to turn the line on or off.

Android:

Go to Settings → Network & Internet to view available lines. Select the added eSIM line. Toggle Mobile Data within the line to turn it on or off. 

(Note: Android displays may vary by device.)

*If you close the line in your home country, the line will be suspended and the home country operator will not charge you any additional fees.