http://www.hvacprofitboosters.com/Tips/tips.html. look at all of these articles. You'll find them extremely beneficial. The one about four column pricing goes into detail on how to set your rates depending on if you waive the dispatch fee once the work is approved or authorized.
As to answering the phone and explaning your posistion, we keep a list of thirty reasons why someone should buy from us next to the phones. You have to overcome objections over the phone just as you do at the customers house.