Default [Q] I9505 with DATA only subscription can't connect to network

Hi estimated XDA community,

I face a weird problem with my Samsung Galaxy S4.

History:
  • I bought it new, operator simlocked, in France
    I use a second SIM from my operator, bound to the data quota of the "main" one, that allows me only for DATA connection
    It used to work at the very begining in pure stock mode (was Android 4.2 by them)
    I flashed several part of it, from CSC to Modem and OS to customize it
    No major crash or problem during any of the flash made mainly with Odin
    Application to change CSC (CSC select, changer, etc.) are usually non functionning
    I could change my CSC to XEF through a flash of stock bootloader and CSC

Current state:
  • The phone is fully functionnal but do not connect to cellphone network (but does WIFI fine though)
    I have signal "bars" displayed with fair reception and it is hooked to my operator network
    I can't issue most of the USSD codes, it ends in a "unable to process request" *#0011#, *#1234#, etc. (but it seems I'm not the only one when running an Android 4.4.2 ?)
    Testing with the SIM card of a friend, who has a standard voice+data subscription, the phone works and hooks the network in 3G
    I changed my SIM yesterday to a new one, freshly activated, to test if it comes from that, problem stayed the same

Network Information tab :
Network : F SFR
Signal : -97 dbm
Mobile Network type : UMTS
Sservice state : in service
Roaming : not roaming
Mobile network state : disconnected
My phone number : unknown

Current configuration :
* PDA : Pure Android 4.4.2 JanJan
* Modem : XXUEMKE

Can it be related to my EFS partition being corrupted?
Is it a CSC problem ?