XPS 9360 CPU overheating issue and technical support issue

Hi, I have a Dell XPS 9360 which the CPU constantly reaches 100 degrees Celcius. 

I contacted the customer service on 5/22/2020 and after diagnosis, the support person "Adhish" told me it may be the heatsink problem since only the fan was replaced under warranty on 10/24/2019 when a fan problem was detected. 

On 5/25/2020, a second support person "Rishabh" followed up and disabled the Intel Turbo Boost in the BIOS of the computer and asked me to monitor the performance of the laptop and give him feedback after 48 hours. However, right after we finished the phone call, he sent me an email and marked that the overheating "issue is now resolved" and no longer responds to my email feedback. 

The laptop processor now can only reach a maximum of 2.5 GHz instead of the designed 4GHz. And very often the utilization stuck at 100% during normal web browsing. I can clearly feel the laptop is slowed down after the "tweak" done by the second support person. 

I replied to the support email thread and a third support person "Mirza Mohsin" replied on 6/1/2020 and said the issue is "related to the software of the computer" and "request" me "to speak to our software support team" and "they will charge a nominal fee" to "fix all these issues." 

I am very unsatisfied with the lack of response to my emails, contradictory answers to the problem, and the transferring instead of solving the problem.