Hey pdk1124, welcome to the community and thanks for posting! Gabe's answer covers pretty much everything I was going to say; I'll also add that for auto-payment, we collect on the day the invoice is generated, but we provide a 10 day grace period for customers that provides them a time frame to make their payment without the service being locked.
Some banks do provide an option to decline any payments if it exceeds your balance; I've had a bank that allowed that option, I've also had banks that do not. To dispute the charge on your account, you will want to call your bank and request them to reverse the payment.
-Brooke
