I never received my September 2018 bill. also, my account shows I'm past due on my last bill even though it was paid on August 2, 2018. Now I have a late charge. I don't think I should have to pay a late charge since I never received my bill.
Do you have access to your online Business Account? Not only can you manage your Comcast Business Services online but, you can manage your bill as well. Visit https://business.comcast.com/myaccount/ or download the Comcast Business App onto your mobile device.
Comcast bills one month in advance so, it's possible when you paid on August 2, you were paying for the previous month's charges. I can take a further look for you if you'd like? Please send me a private message if you need assistance.