Do I need a maintenance agreement?

Tuesday, 9/7/2017, We asked Axberg to come and replace some rusting vent pipe and perform maintenance on our furnace. Axberg replaced the vent pipe, cleaned the furnace, then tells us the heat exchanger is cracked and the furnace should be replaced. Axberg was supposed to send a picture of the cracked heat exchanger but didn’t. Wednesday,9/8/2017, I called the Axberg office and tried to explain why I wasn’t happy with the service. Basically, Axberg charges top dollar and in return I expect them to work smart. Smart is not checking the heat exchanger last! I wanted a break on $444 of useless work performed on the furnace. Axberg wouldn’t budge. I pointed out that now my furnace doesn’t work at all and Axberg still wouldn’t budge. Axberg suggested that if spent more money on my furnace to fix the items identified on their invoice then the furnace would work. At this point, I don’t trust their judgment or customer service. Later Wednesday 9/8/2017, I called another local company for a second opinion. My furnace doesn’t work because Axberg forgot to attach the hose to the pressure switch. I get this fact in writing. Made arrangements for a new furnace install next day. Thursday, 9/9/2017. New furnace installed, not by Axberg. Nice. Called my credit card company to dispute the bill from Axberg. Called Axberg again and this time they at least seemed willing to escalate to a supervisor. I understand that sometimes things go wrong and am waiting to see if Axberg is willing to make this right.