Why do they even bother?

There is a local pest control company that keeps sending me postcards in the mail, asking me to call them to arrange for pest control services at my house. I have called them about four times now, trying to make an appointment for them to come out here and inspect the house, and treat it! But they never answer the phone, I always get their answering machine. I leave a message asking them to call me, but they never return my call! I have to wonder why on earth they are bothering to send out the postcards if they are too busy to call me to make an appointment!