City Grid Media Contract was Cancelled, Got Confirmation but Still billed by City Grid Media West Hollywood, California

We used to advertise with City Grid Media.  Agreement was cancelled because City Grid Media was not advertising as promised. Agreement was cancelled on 08/07/2012 and due to cycle of monthly run City Grid Media Stop running on 08/21/2012 but we were billed for the next month.  Please see below as proof from City Grid Media.

"Dear Mian,This is to confirm that you have decided to cancel your advertising with CityGrid Media. We are sorry that you have chosen to cancel. Keep in mind that we will continue to drive leads to your business until the end of your current billing cycle, which is 08/21/2012. You will then receive your final invoice from us at that point. Thank you.

Please read on for more details: Customer ID:3320Business Name:Swift CopyCampaign Name:Citygrid Fixed FeeCancellation Request Date:08/07/2012Cancellation Effective Date:08/21/2012Budget:350Reason:Comments:Customer Contact:Mian 
(212)683-4900 
swiftcopy@aol.com This customer has no remaining active products for this campaign.Thank you!" 
Tried to work with Mr. Lorenzo Fernandez, Supervisor, Credit & Collections Dept. but he was very Rude, Nasty and Impolite.  Tried to Threaten. Business people never talk/behave like that.