Need to kick a device off my Xfinity Stream

Hi,

Somone is using my Xfinity Stream/TV Go App account to watch TV, movies, etc. I already called Comcast to get this device kicked off and followed their directions of changing my password and setting the 2 prong security thing as requested. I've actually changed my password multiple times and called Comcast multiple times to get this resolved and nobody knows what else to do. This person is still watching my account and this has been going on for months! I've read through the forums and saw instructions about deprovision and even brought this up on the phone to Comcast and nobody knows what I'm talking about. Can someone please help with this, I can see the name of the device being used on the App all the time if this helps. Thank you