Previously unlocked iPhone locked its SIM after Erase

My iPhone 7 was unlocked, I had it for over two years now, used with a UK SIM mainly but I also used it with foreign SIMs when traveling, so I know it wasn't locked to just one operator.

But I recently erased the phone and reinstalled iOS.

Now if I go Settings > General > About > Network Provider Lock > SIM locked

Saying “This device might be restricted to the original network provider and/or have certain capabilities limited. Contact your provider for more info.”

I got in touch with my carrier (Network Provider), their representative said, "SIM card doesn't lock the phones. That's the software on the phone. Sometimes while the phone upgrades, phone gets locked to the SIM that's inside the phone."

I got in touch with Apple, asked them to confirm the activation policy of my iPhone.

I expected them to just name a mobile carrier, but I was surprised to find out the device was locked to EMEA Service.

I found this online: “EMEA Service is the carrier type assigned by Apple for iPhones that have been replaced under warranty.”

This makes sense because I got this iPhone as a replacement phone from my insurance company, so it might have been refurbished.

But what I don’t understand is - I haven’t seen this message before about my SIM being locked, so why am I seeing it now, and what does it mean for me?

I thought it would be the most logical to ask my mobile carrier to unlock the phone, but they pointed to Apple. Apple said the device was not purchased from them and there are no repair cases logged for the device, so they pointed me to the insurance company that provided me with this phone as a replacement two years ago. Apple reasoned that since my original phone was unlocked, but this replacement phone is network restricted, it wasn't a like for like replacement.

Where should I really seek justice for my phone?

Was it erase that broke it? Should people **not** erase their refurbished phones to avoid such a mess, or what should be a general strategy in such cases?