Control screen & navigation issues

I have had issues with my 2021 Pacifica since 1,000 miles. It shut diwn & lost power on the freeway going 75 miles an hour. Now I have continued issues with the control screen freezing & navigation not working. I’ve had loud humming sounds at various times. I’ve had front & side collision sensors go off with nothing next to me. Sometimes the screen wouldn’t turn on so I can’t play radio, use heat controls, Wi-Fi, Bluetooth phone or navigation. It changes all the time. It’s been in dealership 7 times now. One told me not to bring it back because they can’t fix it. I sent Chrysler a certified letter with no response. Any suggestions on how to get a correctly functioning vehicle ?