How do I file a complaint with customer service

Had a horrible experience with customer service. I have currently been on the phone with customer service for 2 hours and 45 minutes and counting.  The first person I talked to thought my issue was related to not having the new Black SIM card. I worked with him to install a new SIM card which took 1.5 hours -- which was a really long time, but he was nice and provided regular updates about what he was doing so I was patient. Then my issue was not resolved once the new SIM was in, so he transferred me to technical support. The person who answered at technical support was the rudest person I've ever spoke with. They didn't say anything out-right rude, but the way they handled the call was so wrong. When she initially answered, I told her I couldn't hear her well. She did not respond, just went silent for about 10 minutes - no hold music or anything. Then she came back on as if we'd never talked and asked me for my name. She was still very hard to hear, so I told her I was having trouble hearing her. She completely ignored this issue and just proceeded on with collecting my information. She did not listen to my concern and kept repeating back the wrong concern. I told her that I was having trouble hearing when I connected to a call and the person on the other line was too -- and she said - "ok so you're having trouble with texting".  Then each time she'd ask me to do something on the phone she'd disappear without notice and without letting me know if she was putting me on hold or just going to do something else. Finally, after we tried several fixes (with very poor instructions and continually going silent without letting me know she was still on the line working on things), she said I just need to get a new phone and that it must be a phone issue. I said, I don't think it's a speaker issue because I can hear just fine when i play a video - it's only when I connect to a call that I can't hear the other person and they can't hear me.  She said NOTHING and just disappeared. This was at around 10pm and it's been about 30 minutes of silence without explanation. I can hear small noises on the other end, so I know we are still connected.  I firmly believe that she just placed me on an indefinite hold because she doesn't feel like trouble shooting with me.  I am so frustrated because I never got her name and haven't even had the opportunity to ask to speak to her next level up and now I really want to because she left me hanging (I think intentionally).  Really terrible customer service. I've now reached the end of this note and I'm looking at the time of this call and it's been a full 3 hours --- 1 hour of which was with this last customer service rep who has only spent a total of maybe 5-10 minutes max actually trying to trouble shoot with me. First Net needs to work on training with its customer service reps.