Access to Incorrect Gateway

I just spent over 3 hours with no less than 5 persons trying to help me. When I sign into my static IP address to access my gateway, someone else's WIFI address and passwords show up. Their devices are also subsequently showing in my Xfinity App as connected devices. I was given the number to a department called Customer Assurity with a phone number that is the general customer service number with the ridiculous dial chain that gets me nowhere. How can I get in touch with this department? Is it a real department at all?