Received new invoice after account cancelled

I requested cancellation of my Comcast business internet bill and worked with the agent, including signing a cancellation request on Jan 3.  I have a copy of the completed DocuSign document for the cancellation, also dated Jan 3.  The agent confirmed that my account was cancelled.  Today I received a new bill for service for the next month and I see no signs that my account was cancelled.  I see an open ticket listed here for my account that says "Retention" even though I went through the cancellation process. 

I will NOT be paying this bill and I am requesting AGAIN to cancel my account.  I request a credit be posted to the account showing that I have no balance due.