Came out to call for a system not heating properly. Customer stated that she couldn’t get the heat to come on properly, and wondered if her thermostat was bad. I checked system over and found the thermostat on lockout and customer was unsure how it got to that. It was also set to 64 on cool and it was 62 in the home. I was able to get the thermostat off lockout and change the thermostat to heat to check the system. Also found the customer had been double filtering the system since she had the home built and had never known about the 16x25x4 filter in the attic. Customer has flat faced grills inside and has been struggling to put filters in them on a consistent basis. Let customer know that we could take these out and just put a 16x25 filter in the attic and then have us change it on routine maintenance. Customer agreed that it would be best to have someone do it for her. I installed a new 16x25 filter in the attic. I inspected the equipment and besides the filters being dirty, surprisi