Why did an app backup to the cloud on my cellular data despite being connected to a local wifi network?

[zach_1]

Why did an app backup to the cloud on my cellular data despite being connected to a local wifi network *and* having the iOS9 wifi assist feature disabled?

I was backing up some of the contents of my phone to cloud storage while connected to my local wifi network. While working on my Mac, I received an iMessage saying I'd used 90% of my data. I thought it was odd, so I checked my phone and the wifi symbol was still on--I chocked it up to heavy usage and a delayed notification.

Then a few minutes later, I received another notification saying all of my data had been used. I checked my usage via the app and site to confirm, and it was true. I was connected to the wifi the entire time, wifi assist had been off (my plan only covers 2gb, I always keep it off), and the app is set to only backup on a wifi connection. What gives? How could it have backed up on cellular connection? Could it be that my phone has some kind of error to display a wifi connectivity icon or to have wifi assist enabled while the toggle shows it's off?

I use an iPhone 6s+ on iOS 9.0.2, and I'm connected to by University wifi network and through a VPN.

[skuibreaker]

same here

[smith6612 · Accepted solution]

Apple fixed a number of issues related to this in IOS 9.1. Apps can and will use cellular data despite the Wi-Fi being connected.

Note that if the VPN was connected before Wi-Fi gained an IP address, the phone may be sending everything through the mobile data connection. This will happen as sometimes the Wi-Fi indicator is a false indicator (old bug from IOS 3.0).

[t-cupps]

With the ios update 9.0 or higher WiFi assist needs to be turned off.  Settings-cellular-WiFi assist turn off.