Unfortunately I can't see what he's doing with the phone. He tells me if he dials a number or uses the phone book it still goes to emergency, so I presume he's not holding the button down. I can see in the handbook that there is an SOS menu and I believe it can be switched off.
Since posting he did say the new SIM works OK in his old phone, which kinda makes me think it's a phone problem and not a SIM problem. ALBA support have suggested a reset and to make sure that calls are not diverted, but he's not too hot with tech and when I try to explain what to do to him, he doesn't really understand what I'm saying.