@MrGregert what device is showing the SSID is still broadcasting? 

@MrGregert I'm also having the same issue.

I had completed a hard reset on my primary Deco S4 (1 of 3) and was forced to set up a completely new Wi-Fi network. My old SSID dropped from the Deco app, but still remains as an available network to connect to with no internet connection via the native iOS and Android OS Settings app. How would I go about disabling its broadcast?

The hardware I have are the following:

Modem issued by Spectrum, which the primary Deco S4 is connected to

Also connected to the primary Deco S4 is a TP-Link 8-port Gigabit Switch

Thank you in advance for your help and assistance!