Late fee for "invoiced" amount that was never invoiced?

Set up a new account Dec 3, got confirmation email right away. Watched for follow-up email on billing but, received nothing.

Just checked account and find a $7 late fee for ‘amount invoiced’ dated 12/24 (Christmas Eve even, how charitable), but invoice was never sent!

So ya, $7 isn’t a lot, but shouldn’t the customer -- in all fairness -- actually be notified (“invoiced”) before assessing a late fee?

(And how to get it removed without spending more than $7 worth of time?)