My viewpoint would be to walk in when the place is really busy and ask to pick up your bike. When they tell you they have not started on it, repeat loudly, "You mean you have had my bike for over four weeks and have not started on it. Do you treat all your customers this way?" Point to someone looking at a new bike and ask, "Will this person have to wait four weeks to get their new bike setup or repaired?"

If they are not totally embarrassed by the way they treated you, get your bike and never go back. The shop is not worth your business.