3rd Generation fire cube Xfinity cable box

I got 3rd generation fire cube to use with Xfinity cable box because I thought I could change channels on cable box because of “built in Xfinity alexa “ compatibility. After setup I am able to switch from fire tv to cable by saying “go to cable”. But when I try to change cable channels by saying ex. “go to cnn” or “ go to cnn on cable” it says that it can’t or it doesn’t have a skill for it. The fire cube is connected directly to the cable box. I spent an hr on with Alexa support trying to fix the issue without any resolution. They told me that the 2nd generation fire cube could change Xfinity channels and didn’t know why it wasn’t working and directed me to contact Xfinity. I looked for Xfinity skill on Alexa like I was told. Didn’t find an Xfinity skill even when logging in to Alexa app with Xfinity ID. How can I get this 3rd generation fire cube to change cable channels? If it’s true that I can’t, then I’m upset because It’s misleading to advertise  Xfinity cable changing capabilities if it’s not true. I feel that I’ve wasted my money. Please help