A-Plus Heating & Air-Conditioning Co they said they would repair a/c but technicians boss called and said non-placeable must replace with new coil Westminister California

I was talked into buying a 3 ton trane air-conditioning unit for $9,788.00 and would last for 15-20 years, with a 10 year warranty.  The warranty expired this year in April 2015 now it's the peak of the heat in August 2015 right when the warranty expired.  I called them and they promised to repair the unit for $129 house call only and I pay for the freon that leaked out of the system which is a 6lb tank at $85 per lb.  I agreed.  The technician came out I paid him and he said I see where the freon leaked out but I don't have my solution to repair it, I have to come back, but I must leave this hand held computer hooked up to your system for 3 days because I can't really tell where the leak is, it's on the bottom I can see that cause it's all black and wet.  I called his office immediately and they were rude and stating they can't control what the technician says.  The technician was telling me just replace the coil for $1100 instead of repairing it because I can't see exactly where the leak is.  So they are ripping me off, they still want their money.  I need them to repair my unit with some kind of warranty, but at this point I don't trust them, they might make something else go wrong, which will cost me to replace the whole darn unit.  Please don't go with these people, the trane product is suppose to last 15-20 years, they have #1 by the consumer report, I guess I got the lemon one.