even though hub is new it is still quiter possible it is faulty and more likely after the work the engineer has done in your home phone customer services and get replacement
assuming engineer turns up see if he has another hub
"Engineer said me today is impossible the hub is faulty because its new device." Any engineer who says that is an idiot.
All ISP's have recieved a faulty batch at one time or another. I doubt very much it was an Openreach engineer you had, sounds more like a Qube engineer who BT use to check internal connections.
It is entirely possible you have a faulty hub, however, it is more likely you are getting line disconnections and the engineer didn't fix the fault. Orange light = no connection. Are you seeing any DSL events in the logs?