Need to remove the xfinity voicemail service

Our landline has an answering machine capability. At some point xfinity voicemail started picking up all calls and none of them are coming through to the phone. It rings, we can pick up to answer but nothing happens and it just goes to the xfinity voicemail. I would like to remove that service since we don't need to have xfinity manage our voicemail. 

I tried to adjust the number of rings when voicemail picks up but that advanced call forwarding feature is not available. I only have the ability to use the base call forwarding which is not what we need.