Need help escalating

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On Jan 8 I bought a Tower desktop through the Amazon Dell Store, delivered Jan 10. I had to deal with a dying family member and was not able to set up until Jan 31. A couple of weeks into using the computer, the screen went black while in Firefox. I thought it might be my new VPN so I uninstalled it. The black screen happened again in Firefox and then in Word, so I started a repair request on March 7.  I had someone work remotely to repair it for over two hours. Four days later it went black again. (I have detailed emails describing all this.) I was then told it must be a software issue and I'd need to pay $107 for Software Support. I did that and got a call 2 days later. This time the person worked for 2 hours remotely and with each change she made, the situation got worse until it wouldn't even boot. My money was refunded and the machine sent physically to Houston, where they reinstalled the operating system. When I got it back, the Windows setup failed twice but finally worked. Within 2 hours of getting software and files on the computer, it went black while working on Word. I have detailed notes of the setup failure. The response to this from Support was 

• The system repeatedly restarting the Windows setup and losing previously entered information may indicate a Windows setup or restore corruption, possibly related to drivers or power management during OOBE.
• However, the recurring black screen with power remaining on, occurring during normal use (such as working in Word) and across multiple setup attempts, may point to intermittent hardware instability.

Dell support had just reinstalled the OS and Windows. This afternoon I had another support call and he discovered that there was a critical driver update needed for the Intel graphics video driver (update dated Jan 24). He  downloaded it, disconnected, and told me to reboot. On reboot I got a green error screen that had appeared several times before during the repairs.

1. If Houston repaired the machine, why didn't they check that all drivers were up to date before they returned it?

2. The machine is NOT repaired and has something seriously wrong with it.

I have requested a refund or replacement and this keeps getting denied because I paid for the machine on Jan. 8. All of the problems started within 2 weeks of setup, and I think that I should be sent a replacement for a machine that 4 attempts have failed for repair. It is obviously defective and it is NOT my software.