Fixed on my side (Orange / France) !
That was surprisingly easy.
I started a chat with the technical support. They asked me for the IMEI. They added it to the database (and also forced it so that it works immediately). Problem fixed ! <3
Edit : well. Fixed for my unit ! But… How to ask Orange to register ALL Kompakts ?
Well. Not fixed. The guy on the hotline did force VoLTE and it worked for a week. Then, it switched back to 3G. He had told me my IMEI was added to the compatibility database but it apparently wasn”t the case.
I am now chatting with another person on the hotline that tells me that… They cannot add the IMEI to the database because the phone is not in their compatibility list !!
I asked how to have it added and they replied : the list is constantly updated with the most common phones models… (so it will never happen !)
Edit : I still have some time thought. 3G will be shutdown apparently at the end of 2028. I thought it was 2026.