I have had VZ auto pay since enrolling 5 months ago, and it has worked correctly. However at the most recent automatic payment date (13 Aug 2012) the system charged my credit card for $0.16 less than the due amount (yes, 16 cents, not dollars), resulting in an account balance of +$0.16. I wasn't sure this made any sense so I contacted VZ customer support, and the CSR also was unable to come up with an explanation. He did however verify that there was $0.16 still outstanding following the most recent auto pay transaction.
This balance is not a material amount and I don't believe there is anything to worry about. I assume it will be picked up on the next billing cycle and all will be well. It appears that I cannot make a one-time payment on the VZ site for an amount less that $1.00, so in the meantime I am tempted to pay the balance using my online checking account just to see what the result is (and also respond to the balance).
I know this is a strange and less than vital problem, but I was just wondering if any other users might have had a similar problem, or might have some helpful comments. After all if the computer can make an error of $0.16, it could just as easily make a much larger error.