Doug, I had similar issues with my Galaxy S8 after an update caused the option to turn off AutoConnect to become grey and unusable. I recently found a solution that seems to be working so far. I went into settings and searched Wi-Fi and selected the Wi-Fi control under the Special access menu. I clicked on Wi-Fi control on the screen it brought me to. Next you should have a list of apps and I went to the bottom and removed the permission from the XFINITY WiFi Settings app.
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