Operating System - I want to file a formal complaint

I am trying to find out how to escalate an issue.   My initial concern was a crack on my system's back cover (speaker).  After I complained that I was not being kept up to date on the work progress that moved from the body to a new motherboard, a new memory card, and other things they claimed to have replaced, I was told that the operating system was not sound and must be reinstalled.   Customer service was condescending, and the manager hung up the phone on me. I need to file a formal complaint but I can't find the appropriate department.