new central unit

my husband had sears come out to give quote on new unit, they draw up papers he signs, not knowing they are putting the balance on a credit card, so what do they do they increase the interest rate. On top of that it's not working properly, for some reason during the winter the unit will not heat, they send the same company out that installed the unit to fix, he gets it working, then summer comes around and it stops working again this is in July they send the same company out, the installer replaces the thermostat with temporary one and says he will be back, that was back in july here it November we have no heat again, he never came back with our thermostat either. i think we have a lemon, so after a year we are to call sears directly for sevice we call make an appointment, sears say they have someone to come around Oct. 27 this was on Oct. 15 when i called, anyway sears calls to cancell because the only available person that can come out was injured on the job???? and wanted to schedule an appointment for Nov. 5th, I asked to speak with a manager or supervisor but was told they don't have a such person that works there. So i ask the rep. in whole state of Alabama you only have one company that only has one Technician that can come out... So its like 65 in my house my husband is a diabetic, you think that company would care, but after I read news of the loses for this past quarter I felt a little happy. So we are now looking to taking them court once we get a lawyer.