Disable Wi-Fi Assist
It doesn't seem like the new 'Wi-Fi Assist' option is possible to configure currently via InTune. Data Roaming is, so I'd expect to see this too?
#me2 (same question)
how to turn off Wi-Fi assist in iPhone try this solution : https://www.howtoisolve.com/turn-off-wi-fi-assist-in-ios-iphone/
Since I can't vote, this really needs to get some visibility. There will be extreme bills if I can't turn this off.
iOS devices. There is a new feature in iOS 9. It will use your 4G data if it detects your wifi network is slow.
Kieran Gupta, Microsoft Intune commented
Can you tell us what platform you're referring to - iOS, Android, Windows Phone?