iPhone 7 4G only working through shared connection

Hi,

I got a new iPhone 7 / iOS 11.3 with SFR as a carrier (French).

The 4G icon is appearing on top (strong signals) but every apps (maps, mail, etc .. ) says i don't have any internet connection.

I tryed some settings reset (network settings reset, complete reset, even factory reset) and nothing seems to work.

Now if i activate "share internet connection through wifi" on my iPhone and i connect a device to my iphone, then this device is able to access internet ! (i can "one device connected" on the iPhone, and see the cellular data volume consumption increasing in the cellular options of iOS).

Does anyone already faced & resolved a similar issue ?

Thanks & Best regards

Guillaume