2002 Honda CRV knocking sound

I have a 2002 honda crv with 217,000 km, on tuesday december 1st, I was driving and just out of the blue my honda started to make a loud banging sound

I parked the crv in my garage and checked my oil, it was clear and clean and did not need to be changed in another 2000km, I have always kept up with my maintenance and my engine had not given me any trouble, none of the lights were lit up to indicate any trouble with the engine

i took the vehicle to performance honda the next morning and they called back and said my motor was gone, either the knock rod or the piston strap and then engine needed replacing

they found another engine with 100,000 and that would cost 1500, plus 1400 for labor. Making the bill 2900.00 plus taxes so I said okay put it in

now they called this monday to tell me that they replaced the engine and it was still making the loud sound and that it was the air conditioner unit not the engine at all.

and the cost for the a/c and the engine would now be over 8000.00 with labor but they would make a deal and I would only have to pay 4500.00

well, I callled today and they are still waiting for the a/c parts and have not started to work on the vehicle yet

in order to repair the a/c they have to tear out the motor again.

am I responsible for paying for the replacement engine when they misdiagnosed the problem. What are my rights? I could have chosen to not fix the a/c or to fix it, but I sure would not have had to replace the engine. Do you know what my rights are?

i really need your help.