LG 1 5 Ton 3 Star Dual Inverter AC - Faulty product

Before * months ago. I installed a new ac from offline retailer l. After installation of ac ac not cooling room from the first day. I ask to retail shop keeper for not working. He just ask to wait for *-* day for proper working of ac. Than I call to LG technical person who installed ac he just ask that ac use only ** dgr. after months, we complaint on LG website. We received a mail for sharing details than after we received a call from LG after *.* months. But he only argued that ac working good. After * more complaint after * months. LG eng. Person check the ac and ask that ac gas leaked or required to fill new gas and service. From the starting ac is faulty. now we demand to replace new one but they refused. Still they are not reached at home for filling gas or any solution.