Apps using Data even if WiFi is active

[Android Central Question]

Hello,
I have a Nokia 7.1 and for almost 20h per day, my mobile is using WiFi connection 100% sure about it.
However last month I've noticed that my data traffic on my O2 mobile account, was showing data connection and consequent use of the data package, in hours in which my mobile was connected via WiFi.

I've downloaded the app GlassWire and I've found out that there are certain Apps that for some reason, on their own (I'm not actively using them) they use the mobile data connection to exchange few data, even if my mobile is connected to WiFi.

For example this morning at 06:48am and 07:50am I've had a connection attempted by:
"Chrome"
"Maps"
"Camera"
"Contacts"
"Phone"
"com.qualcomm.qti etc etc"

Then there's Android System which is using both Data Mobile and WiFi at the same time.

Is there a way to prevent the mobile data usage when my mobile is connected to WiFi without turn off and on mobile data all the time in which I do not have WiFi available?

Thanks,
Erik

 

[Rukbat]

Without manually controlling which one is on? No. An app can be (mis)written to use one or the other preferentially. (There are places where WiFi is metered, but mobile data isn't, so forcing it to use WiFi, if it's available, would get complaints from people in that situation.)

 

[anon(10604040)]

@Rukbat I'm sorry but I don't get you. If my mobile is connected with WiFi my apps are supposed to use WiFi not my mobile data package, otherwise what's the point to connect with WiFi