How to block devices from network

[Sentinel]

I don't know if anyone has ever had this problem, but I noticed a dramatic increase in my usual data usage and after some digging discovered other unknown devices on my network. I changed the password and restarted the router/modem but these devices are still connected somehow. Unlike my devices, these devices are connected via "MoCA" and I don't know how to kick them off my network. 

Any suggestions?

[MediacomSean]

Hello Sentinel. The MoCA filter on your network may need to be replaced. You can send an SMS text message to 66554 to arrange a service appointment for a technician to come out and replace it. If you have never texted with us before, text "join" to 66554. 

[Graciala]

Do I automatically have a MoCA filter?  I am having the same problem:  dramatic increase in usage even though my habits are the same.  I read about MoCa filter, but did not understand it.  Is this something extra I have to purchase or do I already have it ad don't know it?

[Graciala]

Sentinel, what kind of "digging" did you do to discover these unknown devices?  The first time we got the alert about almost being out of data, we did change our wifi password.  Thanks!

[XtreamlyBlessed]

Blocking a device that has already successfully connected to a wifi network with the correct password is not an option with an Xtream modem/router combination device. Changing your wifi password is the only sure method to prevent unauthorized access. The new wifi 360 pro eero system from Mediacom does have this option using the eero app.