Block websites like YouTube/Reddit on Xfinity XB7?

Hi,

I've tried for a few days now to figure out how to block sites like Reddit or YouTube. I've gone to the Xfinity Gateway and added the sites to the block list, but they still appear. I've turned on parental controls both on the gateway and in the app. However, parental controls in the app doesn't allow the blocking of websites. I've tried using openDNS, and set everything up but the sites still aren't blocked. Any ideas from any one would be helpful. thanks :)