I did that too but unsure how useful that informal complaint will be.
Experience from the following Youtube link is he has to go all the way to AZ State Attorney General's Office (17:29) to get Cox to resolve this. This whole process takes 18mon to get Cox finally acknowledges the issue and performs node split.
The author gave pretty good advice at the end: **Start data collection and documenting accurate timeline of communication with Cox regarding packet loss and high latency. I am following his advice now.
Youtube Troubleshooting Your Home Network And ISP - Packet Loss And High Latency