Fetch-a-tech ripped me off Las Vegas Nevada

Last December this company installed a new furnace and air conditioner in my home. The installer knew if would not work properly, since he told me to wait a few days before making a report to the company. The thermostat upstairs and the temperature downstairs were at least 4-5 degrees different, meaning I had to purchase a separate space heater to stay warm downstairs, while the upstairs was roasting. (my old furnace was 1-2 degrees different). I had techs come on a weekly basis for four months trying to fix the problem, but nothing worked. In April I finally told them I was done and wanted a refund/removal of the unit. They initially said of course, but then changed their tune, and now it is July, the air conditioner has come on with an even greater difference in temperature, which can get up to 8 degrees different as the day goes on. I have the thermostat set at 78 upstairs, and it is always at least 4-7 degrees different downstairs. I have again asked for the refund/removal and they sent a tech on July 5, who said there was nothing he can do (he has been here many times before). I had expected the general manager and another lady to accompany him, but they chose not to come. I am really tired of their run-around. I want another company to install a proper unit, but I can't afford to pay them again. I need the refund/removal of the current units first.