"Bait & Switch" refers to offering unreasonably low prices to appeal to consumers and beat out the competition. Upon "baiting" the client, the company then offers services at a much higher rate, citing whatever reason for the change. This is unethical practice.
It is recognized, however, that companies will advertise their price range, and that the client's expectations exceed the lower pricing category advertised. It is also understood that companies may offer limited time discounts or specials on their services.
A good way of ensuring no advertising deception is occurring is to include the disclaimer "All prices subject to change. Inquire for current rates" in your advertising.