iPhone 11 iPhone 11 uses a little bit of 4g lte wireless carrier data no matter what I do while connected on Wifi

[max2]

How do I prevent this ?

No I do not have Wifi Assist on.

 

[bobsamm]

Sounds like you should then lol.

 

[oVerboost]

Enable WiFi assist or manually turn off data when using WiFi.

 

[VineRider]

WiFi assist actually does the opposite of what the OP wants. WiFi assist uses cellular data when in a weak wifi situation. So, you want to turn it off instead of on if you do not want cellular use while on wifi.

 

[adrianlondon]

How do I prevent this ?

No I do not have Wifi Assist on.

I can only assume that the phone occasionally loses WiFi signal and hence reverts to data. Do you occasionally reboot your modem, or walk away from its range? Or maybe your router has "channel optimisation" set, or whatever it may be called. This causes routers to monitor for channel clash and switch channels whenever it feels like. I always disable that option.

There is a bug in iOS 13 (all versions) whereby FaceTime Audio will occasionally switch to mobile data during a call if the person calling has a bad data connection. It's weird. Not sure it affects many people, but it could be the case. Which apps are showing as using mobile data when you check?

 

[jschnee21]

How much data are talking about? It could just be the phone pinging the mobile carrier to say that all is well.

Or a broken app/service that is incorrectly choosing the wrong data connection (not even sure that’s possible — iOS obscures a lot of that stuff)

Airplane mode with WiFi on and Wi-Fi calling is the only real solution.