This happened twice in 1 week on my wifes phone. Samsung Galaxy S5
Got this reply from 48
We're aware of Tesco taking over APN settings. They've been doing this in most Android handsets and we're unsure why they're doing that. We've already raised a case with HQ to get in touch with Tesco to find out why they're doing that and to stop it. This is still under investigation.
Saw someone else reported this in 2016, so I wouldn't hold my breath for a quick (or slow) fix.
Thought this crap only happened while abroad..
Thanks for that idea, I was deleting and creating a new APN.
Did it just now, tesco had come in again today, will have to wait a few days to see how it goes.
I think I've done this before and it worked OK.
I don't remember having a case of Tesco APN settings "taking over" like you describe.
But then Samsung Galaxy phones seem to cause almost as many problems as iPhones due to the stupid way that Samsung/Apple seem to do things.
Hope this helps.
That's a shame.
I don't understand why that happens or why 48 support can explain or fix the problem.
Sorry that I can't be of any more help...