Air Conditioner problems of the 2014 Buick Enclave

The air conditioner doesn't work. I have taken the vehicle in at least 2-3 times and have been told nothing is wrong. The most recent time I took it in was about 4 months ago. Yesterday it was 90 degrees where I live. After school, I pick up my kids 3yrs & 7yrs. After about 5 minutes in the car my 7 year old is complaining of being hot. I look back and she has sweat dripping down her face. This is a safety issue especially for anyone that has infants. After being told my air conditioner is fine multiple times, I don't expect hot air to be blowing out the vents in the back when my air is on. The front was not working well either, but it was cooler air coming out, not cold. I assumed the back was the same temperature. If I had an infant that couldn't speak, they could die from heat exhaustion. This is similar to leaving your child in the car for a few minutes on a hot day. Someone could die. I have also read multiple complaints about the same issue. Please do not let a death happen before recalling this issue. There is a hissing sound coming from the front almost everyday. The air conditioner works sometimes, but it usually takes awhile to get cold or doesn't work at all (usually on warmer days). My car has 60k miles now. This problem started a few years ago. The car was in motion in the city street during this incident.