Update: I changed the passcode as it was ridiculous simple. My ISP can yell at me if they want. Still no change after rebooting. I think it's the ISP it maybe a bad bullet? That's Hubby's territory. He's the cable guy.
5mbps download.

I feel like I'm on dial up.
I still want to know if it's possible to have an unlisted device connected and if so how would one go find it?
It's a NG brand router. I don't own it, it's rented.
I have basic knowledge of the router and its settings. I don't see any misuse of bandwidth. The logs seem fairly clean. I'm writing down all the Mac addresses of my devices so I can keep track. I'm still suspicious to say the least.
Sent from my XT1528