Luckily (or not) in my case the extractor fan always made this odd rattle so I think it was always like this.
Your problem is how to establish fault. Is the noise due to incorrect installation (inc damage to said item by contractor) or is the item faulty due to manufacture?
In your case, as you have not paid the bill yet, get the contractor back and negotiate a deal.
If the contractor will not be reasonable, get another contractor to remove and replace faulty fan, and deduct the cost from outstanding invoice. Just pay the difference.
But you must give the original contractor a chance to do the right thing first.