How to Disable Guest Networks on My Router R6700

https://kb.netgear.com/24097/How-do-I-set-up-a-guest-network-on-my-Nighthawk-router

Manuals are always a good place to start. Visit the support pages:

Support | NETGEAR

Feed in your model number and check the documentation for your hardware.

Check the section in the manual Set Up a Guest Network.

You may have done that already. I can't tell from your message.

I mention it because Netgear gave up on supplying paper manuals years ago and people sometimes miss the downloads.