Cancellation request form filled out July, getting charged for August

I filled out a cancellation request form in July and never received a call to confirm it, even though Comcast's website says "we'll give you a call within two business days to verify this request".  Just today I got an email saying "We've received your cancellation request". This is over a month later. I have been moved out of my apartment since mid-July and haven't used Comcast for the whole month of August. I am frustrated that it took so long for the request to be processed and that I am going to be charged over $80 for a month of service that I requested to cancel well in advance.