What is the mechanism for unbinding the iPhone from the operator?

Question

iPhone

Good afternoon. I have an iPhone tied to a carrier in another country. On the Internet there are many ways to "unlock" it. If the proxy sim technology is completely clear, then how is the IMEI decoupling done? Those. there are many proposals to untie the phone from the operator forever and without using proxy sims, etc. , turning the device into a free-sim. What's amazing is that it works. I don't understand how this kind of connection happens. Secret agents at Apple? Breaking into?
The question solely out of curiosity haunts me for the second week.

Answer 1

It actually happens through the operator to which the SIM card is attached, in fact, most often on his website, and you can make such a decoupling.