I've used Howard Air for a few years now. They helped when I was having numerous issues with the original install company from Tempe and now service my system. I've lived in Phoenix for 50 years and Howard Air's Call Center and Techs are by far the most knowledgeable and honest people I've used.
My favorite tech is Wayne, but you can't go wrong with any of them. I've had a little experience with their Install Department and follow-up was a bit weak, but I will use them when I'm ready for a new system.