Internet Speed Much Lower than Expected

I am paying for the 1 Gbps Internet service and I am currently seeing max download speeds of 320 Mbps. I just replaced the Cable Modem to a Hitron Coda56 supporting DOCSIS 3.1 with the expectation that our wired Internet speeds are closer to 1 Gbps than the 320 Mbps I am seeing. I am testing speed via a device with a physical connection to a 1 Gbps LAN port on the TP-Link Archer C8 access point. The WAN port of the C8 is 1 Gbps and the port on the Coda56 is 2.5 Gbps, thus the current constraint on my side is 1 Gbps. 

How I get in contact with a human being at Xfinity to troubleshoot my service so that it gets closer to 1 Gbps? The AI assistant I am forced to use is not helpful and just making me angry. At some point this has to be turned over to someone who can do real troubleshooting.