F is for fraud. Seasons called with a 1/2 price furnace cleaning offer. The technician said my 23 yr old furnace had a cracked heat exchanger, not knowing the exchanger was replaced under warranty 5 years ago. I called my trusted furnace service, Command Service. The tech used a boroscope (a video camera on a flexible shaft) to inspect the heat exchanger and found no cracks or holes. Complaints pending with IL Atty General and BBB.