Fortnite, among most games, uses either WiFi or Data(on your phone plan). If the person has used all of their data for the month then they will have the option to use WiFi, or if they would like to save Data, they can switch to Wifi. If your goal is to maximize the Xfinity service of pausing, then your best solution is to remove Data from your child's phone plan completely, or limit Data on phone plan to a very minimum amount, such as 100mb/month. Fortnite is a data resource intensive game (and only plays online) and 100mb will be used up in less than 20 minutes. That way they MUST use WiFi to play games at home and therefore you will have pausing of games functionality as you so desire. Keep in mind that pausing WiFI on games does not pause the game, instead the game will close when the WiFi is paused, just like if your WiFi shut off while you are in a game or online researching.
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