Can’t pause any device

Good Guesses!

Your statement of the obvious, "... device and people you do not know about on your network." is truly unhelpful! 

What if your suggested User Actions were already performed (except the usually frustratingly futile call to CSA) and the issue reappears? 

I am guessing that the User would have to do a forensic trace to determine the culprit(s), 

if the User has that Technical skillset, or find a well-skilled tech to do it for them. 

I wonder if some expert hacker has defeated Concast/xfinity Modem Security? 

Another possibility that I can envision is a hack allowing

compromised access to the User's Device(s) to determine their SSID and Passcode(s). 

Which is more likely?

Probably, unfortunately, the average User has a less robust level of

Device Security and knowledge about Cybersecurity than Concast/xfinity. 

But yet I wonder ... .