Removing SSID not shown on SBG6580 modem (Motorola)

Some time ago I heard about splitting one's wifi into two spectra for less interference; a <SSID>_2gext and an <SSID>_5gext. I did it, and my modem promptly offered 3 wifi names for connection: SSID, SSID_2gext and SSID_5gext. I used them for a while, and a year or so ago I deleted the _5gext wifi. Now I want to remove the SSID_2gext, but find I can't. At the Wireless - 802.11 Radio page in admin, I can select a 2.4 gig bandwidth, or a 5.8, but cannot select none or both. My Wireless - Primary Network Settings only shows SSID, it does not show SSID_2gest.

The Arris website has nothing on this. Google brings back nothing that I can see as useful. How can I get rid of the _2gext network and go back to my plain SSID network?

Running Ubunto and Win7

The MODEM is a dual band device i.e. has separate 2.4 GHz and 5.8 GHz WiFi capability plus a guest network. If you click wireless on the web configuration menu bar you should be able to disable the 5.8 GHz and guest networks although I could not find the exact steps in the manual but I only scanned through the document. I believe you can go through the wireless setup wizard again to reconfigure it as desired.

http://arris.force.com/consumers/Con...and%20Gateways

Thanks, I'll read it again and see what I'm doing wrong.