NO Internet

[Greg T]

If i got to "Settings", turn "Network & Internet" to "ON" ... it turns itself off, within a few seconds & I can't get it to stay om.
How do I fix this?

NOTE:
1. I recently had the phone repaired it was doing this before the repair & it's still doing it. { P.S. Actual repair job was very good }
2. I took the phne to my network provider (EE) & they said it was nothing to do with them, I was paying for 50Gb of data per month, but not getting it & "not theor problem"
3. I can get wi-Fi, if available & logged in, but that is not the problem

[Greg T]

CORRECTION / UPDATE

The "settings" menu says:
"Mobile Data is off - Internet available only via wi-fi

I press "Turn On" ...
And between 5 & 30 seconds later, it's turned OFF

 I've now told it to access via wi-fi, but hat still won't work if there is 4G signal, but no wi-fi.