How to escalate an issue when manager doesn't call back

I bought a Dell Inspiron 7791 2-in-1 laptop from Best Buy on 12/14/19. I reported a problem with it crashing with a black screen on 12/8/20. After much debug the tech support person told me it had to be a S/W problem. I asked him to escalate the issue and he said he couldn't. We continued to have the problem more and more often until yesterday it was happening once an hour and wouldn't reboot for an hour after it crashed. Today it will no longer power up. I called yesterday thinking that since I reported the issue while the computer was still under warranty (expired 2 months/14 days ago) and the issue was unresolved that now that it is clearly a H/W failure it would be covered? After getting transferred I believe 9 times (once back to the ADR) and getting hung up on once, I finally escalated it to a supervisor and then to his manager. I was promised a call back today and never received it. I paid a significant premium for this computer because up until now my experience with Dell support has been good. Now I am frustrated beyond words. My daughter needs this computer for school and now it's basically a paper weight. Is there a way to escalate this issue to someone who cares and can actually help?