They are salesmen, not servicemen.
Dealing with them is like reading the Book of Revelation. Everything is the Apocalypse! "Well, this water heater won't last another week. Your garage will be flooded, and I'm worried your pets may drown. You should either build an ark, or hire us for... $15,000. Your call sir." (Months later it still works quite well)
We also were told to replace our entire air conditioning system for thousands of dollars, but we fixed the fan for $100.
Also, they attempted to charge $500 for repairs to our heating, and we had it done by a competing service for $60. Sixty dollars! They missed the easy stuff, and default right to replacing your entire system.
Using them is like throwing your money into a furnace. They are exceptionally expensive, and inefficient. It's either a scam or ineptitude.