Xfinity has now charged me $250, even though I canceled my contract

Your system sends me a bill every few days with a different amount; the last one was for $250. I canceled your service three months ago, but I’m still getting bills. Your staff is incompetent. Explain to me how it’s possible to cancel an internet service and still receive emails with bills for the next three months. At the time of cancellation, I had paid all my bills for the entire billing period—I checked this with one of your employees, and they confirmed that I had no outstanding balances. I haven’t lived at that address since July 1; someone else has been living there since then, yet I keep receiving bills every month—they’re getting higher, and your system keeps sending them to me every few days. 

@mariuszess Our team would like to help resolve your account and bill concerns. Can you please direct message me your first and last name along with your full service address so I can assist you further?
To do so, click on the chat icon located at the top right of this forum's page.
Here are the detailed steps to direct message us:
• Click "Sign In" if necessary
• Click the "Direct Message” icon (upper right corner of this page)
• Click the "Start new conversation" (pencil and paper) icon
• Type "Xfinity Support" in the "to" line and select "Xfinity Support" from the drop-down list
• Type your message in the text area near the bottom of the window
• Press Enter to send your message

I hope you see this message. 

I hope you see this message.