When we moved house we had to have 2 engineers because the first one came and well didn't have to do much apart from fit a broadband point in the dining room because the living room was already cabled, then when he went he said he was going to the exchange to connect the phone and he would ring to tell us he had done it, didn't happen, was left with no dial tone still, only now when you rang the house you heard the calling tone but the phone didn't ring. So rang Virgin, sent an engineer explained there would be a charge if it was our equipment blah blah blah, engineer didn't turn up at the house BUT, got a phone call on the landline with the engineer saying 'Right, done it!' so obviously the first one had connected us up wrong.
So basically the moral of the story is the engineer needs to go to the exchange to activate the phoneline at the exchange (which in my case, the first one did but probably connected it up to the wrong house)
Hope this helps,
Ben