Ok so I’m quite happy to be told I’m a numpty but I’ve just got my phone today, put my SIM in, all fine.
I’m with EE/ Orange, but, on the very first start up screen of my phone, it says T-mobile UK, right under the unlock symbol…eh?? Why so?
Hi @BurnerBee
First of all: welcome to the Fairphone community! Did it say “EE” or “Orange” on your previous phone? After doing some research I’ve learned that EE is a joint venture between Deutsche Telekom and Orange and is formed after merging T-Mobile and Orange businesses in the UK. So, odd as it may seem, this probably isn’t a problem. EE probably uses cellphone towers owned by T-Mobile, hence the “T-Mobile” sign.
I found this article on the internet. Summary in short: more ‘modern’ devices are being updated to show “T-Mobile/EE” in stead of “Orange”. Your previous device probably didn’t recognise the change in name 
Nothing to worry about.
I hope this solved your question
Kind regards,
Robin
Had the same thing years ago with my gf who was on an Orange prepaid subscription. One day it was changed to T-Mobile because of the merger. The whole thing was rebranded T-Mobile so she had to buy T-Mobile prepaid vouchers as the Orange one disappeared.
@BurnerBee - Yeah it’s not a major issue. It’s down to the way EE has merged their networks and the way phones are programmed to understand what network ID equals what network name. I’m stilling picking up T-Mobile for my work sim, whereas my colleagues show the SIM as EE. It’s nothing to worry about anyway
Many thanks all, appreciated.