Letting agent is not too professional

The agent Kelly who manages my property is good and that is why I give my property for her to manage after occupying the property myself. However, I am not satisfied with the agents who came and show my property. They came late two times on viewing and one time just on time. There is no sign on the street that the property is for Inspection during the visit. They don't know too much about my property beforehand and don't know where is the car park. I expect they came earlier on the first time they show my property. It took over a month before my property was rented out.