Beyond annoyed with the customer service

Hey everyone! Need advice or help on what to do before I just drop this account and find a new ISP. Long story short I am using my own modem and router combo. When setting up the cable modem It requires certain signal levels. I am using the Arris Surfboard SB8200. The signal levels required for the downstream require at least 3.0 dBmV and xfinity has mine set at 0.1 dBmV on almost all. The uplink need to be at least 45 dBmV and is at 43 dBmV. After three support tickets I not only feel disregarded but mocked. Am I able to input these my self or can a rep who understands what I’m asking for properly help me with my service. https://arris.secure.force.com/consumers/articles/General_FAQs/SB8200-Cable-Signal-Levels