Do not give your credit card to the technician over the phone because your number will be written down to be entered later, which is unsecure. Also, ask for a detailed breakdown before agreeing to large repairs. When I asked last summer why two $20 air filters cost $200, they said they were going to leave 8 extra behind (weird). When I asked this month for a breakdown on a $900 quote to replace a heating unit motor, they said it was an odd request. Emailing quotes proactively would be a nice improvement.