My phone is constantly sending and receiving data, why?

[userouFrgEIbLW]

I have T-MOBILE and I just factory reset my phone. To my knowledge no APPS or location services are running.  And my mobile data is off.  The only app I have running, that I installed myself, now is Proton VPN. 

Despite my mobile data being turned off and only connected to WIFI I get a constant 300+kb downloading and it is constantly uploading data around 200kb.

Why is this?

[userouFrgEIbLW]

It fluctuates, so I tried my best to catch it.

[userouFrgEIbLW]

It constantly every few seconds sends an upload at around 200b/s.

[LongHiker]

Do you have any email client set up?

Email services check for updates in the background constantly.

Pretty much any social media app checks for updates in the background so it can pop you Notifications.

Do you have Googe drive or OneDrive configured to back up photos?

I dare say thousands of apps check for updates and notifications in the background.

BTW, you may find the app Glasswire useful for determining which app is using data.

[realaud]

Do you believe the VPN does not send and receive data in order to remain connected? Are you sure those are not wi-fi data runs.  If you are on wi-fi, everything should run through wi-fi.  You can check if your mobile data is being eaten up in the connections/mobile data settings. As @LongHiker  says, email is always checking, Google services are always looking for app updates. If you have mobile data off, nothing should be streaming through it.  Your VPN will work with whichever data stream is active at the time it is in use.  The data stats you see are coming through your VPN, which is protecting your Wi-Fi network, which you are currently using.