Is a device using large amounts of bandwidth without an explanation, or do you just want your teenage kids to come to the dinner table? Whatever the reason, temporarily blocking the internet connection will do the trick.
Go to Devices ➝ Menu
Locate the device you wish to block the internet connectivity for
On the right-hand side of the screen, locate the Block button and click it
Internet connectivity for the selected device will now be blocked until you manually unblock it.