Hello Pam, go to http://www.mitsubishicomfort.com/ and enter your zip in the box. This will show you the Heating & AC companies that serve Atlanta. Diamond dealers are ones that have gone to more factory training and purchase more Mitsubishi equipment (the other companies may be good too, maybe too small to be diamond dealers though). I recommend doing a little research on the companies because quality workmanship and installing/designing the system correctly is vital to a problem free system.