Well what do you expect all they are interested in is making money,along similar lines, just look at a credit card statement if you use your limit 1 month and then wait until the payment has been taken from your account but the same day use your card (say late at night, after they will have taken the payment) they add over-limit charges
something like this
card limit £1000 spent £1000
payment due date payment taken date
1st of month 28th of month
on the next statement they say payment was received on the 28th but you used your card at 23.55 on the 28th now they will have taken payment earlier in the day but your use of the card will appear on the statement before the payment they receive so they add an over-limit fee. it has happened to me but i have always got the fee refunded.
Like i said earlier it is all about money and they don't care