Xfinity Cable Modem with WiFi LAN

When the Xfinity Cable Modem was installed, our secured home WiFi appeared on our computer's available WiFi networks list as secured - which is good.

But, another WiFi network labeled as "xfinitywifi" that is unsecured also appeared on our computer's WiFi network list.

When we removed the power from our Xfinity Cable Modem, both our secured home WiFi and the "xfinitywifi" unsecured WiFi disappeared from our computer's WiFi network list.

This means that the "xfinitywifi" unsecured network going through my Xfinity Cable Modem and could increase my Xfinity data usage if someone connects to it.

How can we disable the"xfinitywifi"unsecured connection that is going through my Xfinity Cable Modem and still keep my home secured WiFi running?

Thank you.