C7800 — Nighthawk X4S AC3200 WiFi - C7800 issue

[Astraleon]

Hi all,
I have a 900mbps contract with Xfinity.
My iPhone's 5G wifi connection is unusable. Speedtests usually have a result of 1mbps. Sometimes I get "network unavailable" even though it is connected.

Xfinity has stated some BS reasoning claiming it is my modem's fault because my internet package is too fast. NETGEAR support basically is of no help either. I cannot find a solution. This issue basically started happening when I moved to my new apartment. Before the move, I never had an issue with the 5G band.

The 2.4G band and wired connection work fine. I've tried basically every troubleshooting possible ie. Resetting the modem, changing channels, resetting network settings on devices, etc. all to no avail. Does anyone have any advice?

[FURRYe38]

FYI, any wifi device connected on 2.4Ghz N mode or 5Ghz AX will never see anything near 900Mpbs. 

2.4Ghz I've ever seen is around 100Mpbs to maybe 200Mbps depending on how good the device is designed and supported. 

5Ghz devices top out at around 300-500Mpbs on 5Ghz on 80Mhz with 2x2 MIMO. If a device supports 4x4 you may see higher speeds closer to 900Mpbs. If the modem supported 160Mhz, and you had a 4x4 device, then you would need near 900Mpbs on 5Ghz AC. I don't believe this modem supports 160Mhz.