A.E.S. Sales & Services Sdn. Bhd. (Johor) — Poor services

I'm writing to complain about poor service provided by A.E.S. This company is authorised as Panashop i.e. authorise dealer to distribute Panasonic brand products. I've purchased 4 units of air con, 2 units of water heaters and 1 unit of Fridge from this company during the Furniture fair at Persada on last Sun (22 Jun 16). Unfortunately, I came to learn from my contractor today that it's not feasible to install the air con. for one my rooms. I've no choice but to request to return or exchange the air con with other Panasonic product. To my disappointment, I'm not allow to do so despite the air con. is yet to be unpacked and it's less than 7 days from date of purchase. Reason being is the tax invoice has been issued. This is truly unacceptable from consumer point of view.