It may be worth changing agents depending on the property you are trying to sell. Some Agents get lots of lower end starter homes on their books and will have people on mailing lists waiting for that sort of property, some agents have more rural properties and different clients. Make sure your property 'fits' in with the other houses the Agent is selling -if not do a search on line of the particular type of house you have for sale and see which Agents have sold the most.