The forums are mainly a customer to customer help forum. No Comcast Billing or Customer Service Reps read these forums to answer these questions.
To find out about the past due payment you will need to call Comcast at the 800-COMCAST number and ask for Billing about this.
Also be aware that Auto Pay would take up to 45 days to become active and many people have reported issues with auto pay not processing payments, double payments taken out, etc. The general feelings of a lot of people is don't use the Comcast Auto Pay.