If it has not been removed as a feature by the TWC firmware, it must be in the wireless section of the configuration pages, most likely in the advanced section, and you may have to hunt through wireless page by page.
I suspect that it could have been disabled though because looking at the TWC manual wireless configuration main page I did not see a choice over on the left side for advanced. Compare page 57 of the TWC manual
HERE to the basic Ubee guide for the device
HERE.