BE18000 RS600 Tri-band SSID Issue

I just bought the BE18000 RS600 Tri-band WiFi 7 router and no matter what I try during configuration (either Web or Nighthawk app) I cannot disable the SSID.

Using the Web interface I uncheck the SSID broadcast option - but two of the network SSIDs are still being broadcast. I have rebooted the router also, to no avail. 

How do you turn off the SSID broadcast? 

Any help would be greatly appreciated. 

Many thanks!