LG Air Conditioner Not Cooling, Support Service Unresolved

On June 13, we purchased an 18,000 BTU LG inverter air conditioner for our 24-square-meter room from Media Markt. Installation was completed, and we began using it. However, we were dissatisfied with this air conditioner. We used it for several weeks, and during this time, it failed to cool the house even at room temperature. Due to the heat, our baby continued to experience discomfort. Regardless of the temperature setting, it could only reduce the room temperature by a maximum of 3-4 degrees. When the house was at 32 degrees, after turning on the air conditioner, the temperature only dropped to 28 degrees after 6-7 hours. If you sit in front of the air conditioner, it provides a slight refreshment, essentially functioning like a fan. Even with balcony doors open, the house remains equally heated. We called the technical service, and an employee put his hand on the air conditioner's air outlet, claiming it cools sufficiently, and there was no issue. We requested a gas level measurement, but again, he visually checked and said everything was normal. I mentioned that such a method is not accurate enough, and finally, they measured it with special equipment and again claimed everything was fine. They were very rude, with an ironic tone, and we had a heated argument. They stated that the air was very hot and humid, and the air conditioner can only cool to a certain temperature, and everything is normal. If we hadn't used an air conditioner before or didn't know that neighbors' air conditioners cool their homes to icy temperatures, they might have convinced us. They refused to prepare a report due to our dispute, saying we should take action ourselves. We suspect there is a technical problem or a factory error in the device. Since the weather has cooled, yesterday I ran the air conditioner again in cooling mode for a few hours and could only reduce the room temperature by 2 degrees. We spent 20,000 ₺ on a device that was of no use to us at all. We were satisfied with other LG products, but this time both the brand and its service were a big disappointment for us. Our summer, despite having an air conditioner, passed in heat, and we suffered. We demand support from LG for a defective product, and if a refund is not possible, then a replacement for the product.