I suppose all these ID confirmation demands are due to dishonest scammers having a go. There have to be safeguards in place or they'd have the skin off your back and pinch your identity.

I don't own a 'phobile moan' - can't stand the blooming things and I've never needed one. Also there's a pathetically poor signal in our village. But whenever I fill in some blessed form online/buy something the thing demands my phobile moan number. If you don't have one the page refuses to pass onwards and goes all red. I've learned to type in a made-up number.