Windows 10 Delete old available networks [Window 10]

My cable company changed my router. I'm trying to get rid of some old available networks. [I also have an extender] I've forgotten them everywhere, including the settings and Command Prompt. When I go to Manage known networks, they don't show. But when I tap the wifi button on the system tray, they still show as available. Any suggestions??? [same thing happens on my Galaxy s20 5G - I forget and they still show]