Slow Speeds NG C7000 AC1900

[rbarnes_93]

My Xfinity plan is 800mbps download and I get anywhere from 175-275mbps on my C7000 Nighthawk modem/router.  Xfinity came out with one of their routers and got 600mbps.  I have tried factory resetting my modem and still have the same issue.  NG techincal support said there are not any hadware issue with my product.  Any ideas on other possible solutions? I have had this issue since is first used this modem/router.

Thanks!

[FURRYe38]

Are you speed testing with a wired or wireless device? 

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 then back ON.
https://community.netgear.com/t5/Cable-Modems-Routers/General-info-and-Troubleshooting-for-Cable-Mod...