I got a C7800 and cannot get the speed I expect.

[SkyNet6]

I have a Netgear Nighthawk C7800 that is not getting the proper speed. I’m with Xfinity/Comcast and have a GIG subscription. The came out and tested and I’m getting 1.2 GIG from the wall. All test I do only get 500-550mps. Any Suggestions?

[FURRYe38]

Are you ethernet connected with a PC or laptop at the modem? 

What speed test tool are you using? Ooklas installable speedtest app is recommended. 

[SkyNet6]

Hardwired to modem. My wireless devices get up to 600mps. ????

[FURRYe38]

Please post a copy and paste of the modems connection status page.
Have the ISP check the signal and line quality UP to the modem. Be sure the ISP provisions the modem correctly.
Be sure there are no coax cable line splitters in the between the modem and ISP service box. 
Be sure your using good quality RG6 coax cable up to the modem. 
Be sure to power OFF the modem for 1 minute them back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...