Broken seatbelt

Hello everybodyyy. I had a terrible experience on an aa flight on Sunday. Im traveling with my sister and we both are in middle seats across the aisle from each other. I sit down and try to buckle, and the buckle barely goes in the latch. I try forcing it a few times, but it pops out every time. This caught the attention of the woman next to me, so she tries to help me to no avail. She flags down a flight attendant and explains the situation. I look up at the flight attendant after fidgetting with the seatbelt a little more and before I can even get one single word out, she says (very rudely and frankly sarcastically), "I don't know what you want me to do. You want to file a complaint? You want a new plane?" I was floored. After a second I said no and that I personally was okay with the seatbelt not working (which I probably shouldn't have said, but too late now. I didn't want to get on a new flight) but, reiterating, the seatbelt does not work. Because I thought that was probably a big deal on an airplane. This catches the attention of the people in my sisters row across the aisle, to which my sister speaks up and says her seatbelt isn't working either. The flight attendant barely glances at her before she leaves and brings another flight attendant with her and they both look extremely annoyed. They offer me a seatbelt extender. I clipped it on and tightened it as far as it could go and it was about 8 inches from my lap, so, obviously not going to help in an emergency. They both just stare at me and then walk away. A minute later the original flight attendant comes back and says "I'm not supposed to tell you this..." And goes on to say that because of the partition between our seats and the seats in front of us, the seatbelts in the middle seats of both rows my sister and I were in just don't work. They didnt once try to help my sister. I don't really understand how such a big airline is letting this happen, or any airline for that matter. Is this not a huge liability for them? I am going to file a complaint, but is there anything else I can do? This is just crazy to me.

TLDR mine and my sisters seatbelts didn't work on aa flight, flight attendants were extremely rude and sarcastic about it and did not help.