Billing Issue - Stacked NSF & Late Fees After Failed Payment Notification Error

I need assistance from a corporate supervisor regarding an unfair $75 fee stacking issue. I changed bank accounts, and Xfinity's automated system never sent an email or notification that my July 21st payment failed (through the old account). Instead, a second attempt was made on August 4th without my knowledge, resulting in $75 of stacked late and NSF fees. I have been a loyal customer for 1.5 years with a perfect payment history. When I called the loyalty line to ask for a supervisor, the agent hung up on me. Please help."