How do I file a claim against the Xfinity Custoemr Service Guarantee

Xfinity pledges a custoemr service guarantee.  They even have "TOm", the head of customer support, who commits to this pledge.  But there is no place on thier site (that I can find) where you can actually submit a complaint.  I am SO FRUSTRATED with their customer service!  The Bots on text and on their chat feature are not helpful!