How to forget (remove/delete) these saved O2 Wifi networks?

[idkwho]

Hi I am having a lot of trouble with trying to remove these four O2 Wifi networks from my Samsung Galaxy Tab S4 Tablet (WiFi only version). 

I have tried: Reset network settings and Factory data reset but these saved networks remain on my device.

There are four saved networks:

O2 Wifi

O2 Wifi. 1x

Wifi Extra 

Wifi+

The problem I have is that there is no forget button to remove these Wifi networks as can be seen in these screenshots:

[MI5]

They are part of your O2 account and cannot be removed.

[idkwho]

I don't have an O2 account is there a way to remove them from the device? How were they added in the first place?

[MI5]

It must have o2 firmware on the phone then.
The only way is to reflash generic firmware.

[idkwho]

It is a Samsung Galaxy Tab S4 Wifi Only Tablet device which is already on Generic firmware (BTU). I have tried factory reset and reset network settings but no success.

[MI5]

OK, so have you ever had an O2 account, or connected to o2 wifi previously?
Are these saved to your Google account, if so, they will be remembered and saved to any device you login to.

[Bambino]

@idkwho You might want to contact Samsung support directly. https://www.samsung.com/uk/support/

[idkwho]

I bought the device used from a previous owner and asked them if they had an O2 account which they said they did not.

I have factory reset the device without signing into any google/samsung account but the saved networks are still there.

I'm trying to figure out if there is a way for me to remove the saved networks perhaps by going to an O2 Wifi hotspot and registering an account to use it. But I've never been an O2 customer so do not know how it works (how these four networks were added - was it through an app?) and if it would allow me to delete these networks.

[MI5]

Someone, at some point has connected to O2 wifi or installed the O2 wifi app (which no longer exists).
I don't know of any other way of removing them, but they aren't doing any harm being there.

[idkwho]

Just wondering, if I connect using the O2 Wifi app (I have the apk) is there an option to delete these networks within the app or if I delete the app after connecting to the hotspot will it remove the networks?