xfinity services not turned off on cancelation date and billed for the next month

On 8/1 I put in my cancelation request for my internet service for 8/31 and received multiple confirmation emails. On 8/26, I received a bill for services 9/1-9/30, which I should not be paying for because of the cancellation. However it is 9/1 evening, and service have not been turned off, and this bill is still on my account. I will NOT be paying for these services, as it was not my fault that xfinity did not do their job in turning off my services when given an entire month notice. FIX THIS!