Thank you guy for your help , but now I've discovered that this Lumia 920 is 'Orange France Sim locked'. It does not work with any aother different sim.
I suppose that flashing rom is not the solutions to 'sim-unlock' this phone.
Looking around I found many sites that can send me the unlock code but I don't know if they are safe and secure.
Do you know any secure site that can help me... obviously I prefer the cheaper one.
Are there any another way to sim-unlock my lumia? using 3rd party software or something else?