Terrible online bill-pay, phone customer service, and options to file a complaint

Comcast Business' online bill-pay is the worst of all online bill-paying services I use for utilities, banking, etc.  Every other account allows me to input payment account information, which is then saved.  WIth Comcast Business, I have to re-enter it each time.  The last time, I entered the information incorrectly, which caused our payment not to be registered (although I got a confirmation number).  Unfortunately, this was after I accidentally did not pay my bill the previous time.  I'll fully admit my error, excused only that I'm working out a temporary office and that the bill was misfiled after being copied for an expense report.  I do not pay my bills late, and my history with Comcast, both business and residential, would show that.

When I called customer service questioning why there was no record of my payment for both months, the woman I spoke with had real attitude, would not give her name, and said she didn't have a supervisor when I asked for one.  She acted as though I were a criminal who always paid late, and started to patronize me by calling me "Ma'am."  After looking everywhere on the website, I found no way to file a complaint other than this forum... or to call customer service again.  Sorry, I already tried that route.

I've been irritated with the online billing since I started using it.  Nowhere is there an option to set up email warnings that my bill is coming due or that I have missed a payment (all available with every other online bill I pay).  If either of these existed, I would have noticed my initial error when things were going a little crazy around here.  Should I just use auto-pay?  Not after the forum posts I've read here.  Unfortunately, Comcast has a monopoly on business internet where we're located.  How convenient.