SIM-locked iPhone, but...

Recently I bought an iPhone XR in a foreign country because of reasons I won't explain given they're irrelevant to the whole story. When I arrived to my home country, the phone couldn't read neither physical SIM nor eSIM cards and you will think this iPhone was stolen or reported as lost.

The problem is this: First, there is no SIM restrictions attached to this phone. We run external tests with the IMEI to verify what iOS already said and that's the case. Second, the vendor provided direct information from the national registry of stolen phones in his country, and the IMEI doesn't show any restriction attached. Third, my home country signals that the phone is able and ready to be used with local networks without any problems. Fourth, we know for a fact that this isn't physical damage, given that eSIM doesn't work either and the other network capabilities of the phone -Bluetooth, WiFi- work just fine. Fifth, I verified the SIM in my principal iPhone -iPhone 13 Pro- and it works without any problem.

What can we do about it? Is there something I haven't look upon that I should know about it?