late fees and return fees

i’ve been enrolled in auto payments for 2 months and both bills charged me late and return fees. when contacting customer support i’m told it’s my banks fault and get hung up on. i’ve verified auto payments with my bank and i’ve spoken to xfinity customer support 7 times. i’ve also made successful payments to xfinity after being told the first time was a “technical error”. how would scheduled automatic payments be late? why are technical errors happening every billing? feels like xfinity wants to take advantage of their customers and if/when it happens again next month i will have to cancel my service and find a better internet provider