[TrudyM]

Comcast has turned the modem in your home into a mobile hotspot for their other customers use. Now it is a separate line so they can't see what you are doing but they are using your bandwidth and electricity. I have noticed that my internet access in the rental I am at slows way down at certain times of the day. Called Comcast and the guy said others on the public side of the modem were using it . Mystery solved other people are logging in and gobbling up the bandwidth.
HOW TO SOLVE
You can log into your account at Comcast Then click Users & Preferences-->Service Address, which will have your address. Underneath your address click Manage Xfinity WiFi, and then click Disable Xfinity Wifi Home Hotspot. After that, click Save. Now if you see xfinitywifi show up again on your available connections it means that Comcast sent out an update and it turned it back on. Go to Comcast login and turn it off again. Sorry to say I can't do that because I don't have access as I am in a rental but maybe the info will help others.

I don't mind being neighborly but sharing my connections so I can't get on is not acceptable.