Delete Wi-Fi network on 5G Gateway

I have T-mobile's home internet with their 5G Gateway. I am unable to delete the wifi network, as it says at least 1 network is required. I have my own router connected to it as I have multiple devices physically wired to my router.

The issue is that due to the gateway and router being very close to each other, the gateway's wifi is causing interference to the router's network being broadcast and thus causing lower speeds.

I with T-mobile would just let advanced users delete the default network. Anyone have a workaround for this?