Programmers, who're aware of Smartphones.

[Tutashkhia]

According to this thread, you should try Lumia Software Recovery Tool, downloaded from this official page. Follow instructions on that page.

If this doesn't work then I'm afraid that the network chip on your phone's motherboard is damaged (information from the first link I provided).

PS: Trivial question, but have you tried taking your SIM out and putting it back, placing it correctly?

Tried that like 1000 times. My SIM works on other phones, I even tried putting other's SIMs, but none worked.

What's about that program, I tried some programs of that kind and all of them were same (updater), but here's a problem:

Can't start the update.

P.S Tried NSU (Nokia Software Update) and it showed the same too.

P.S.S I even tried launching that program, plugging the phone, pushing the "shutting down" and "turning down the volume" keys, but the phone started updating itself. But nothing happened... same problem.