XPS 13 9370 - Customer Service Problems

As a researcher and teacher at a University in France, I have huge problems with my laptop and the customer services for almost 1 year. 

In the beginning, my wifi card was crashing from time to time, and the sound was crashing as well. Then, with the confinement, I started to do all of my courses online and I couldn't stand these problems, because just think about it, I am giving a class and wifi crashes, or sound crashes. So I opened a ticket.

1- For the first time, they tried all the solutions for the sound and the wifi, but they couldn't fix it, so someone came to my home and changed the motherboard. After the new motherboard, the wifi was not working at all, my fans were working like crazy and the power button was not working at all. So, I opened another ticket.

2- Second time, a responsible came and changed the motherboard again, he was all mean! He ruined my laptops backplate screws, lost one of the screws and now there is a missing screw. The other screws are irreparable now as well. Additionally, I have the sound problem again with constant electrical noise and it continues to crash; my battery is finishing way faster than before and the laptop closes itself with 20-30 percent of battery, and the most annoying part, my screen is flickering in different colors, such as yellow and blue. 

The customer service informed me that "they cannot do such of motherboard change anymore because of the fact that they did it two times and the problems still exist; so they need to move this subject to the upper managers". As of today, I have emailed him twice about the I have still no information about that ticket.

The main problem is that, when I chat with the customer service, every time, they are all making me the same tests again and again and they want me to re-record all the sound and screen issues but I cannot because these problems happen from time to time. By the way, I sent these kinds of proofs to them before.

So here I am, demanding a proper Customer Service. All I want is a not-crashing laptop. You changed the motherboard two times, and my problems are increasing in the place where they need to disappear. You cannot imagine what kind of problems I had in the online classes because of my faulty laptop. I all the time have serious communication problems for all my online seminars, online conferences as a researcher in my professional environment and again with my students.

Ecem.