If I change my iTunes payment method after making a purchase, which one is used? As explained here, there is often a delay of anywhere from a few hours  to a couple of days between an iTunes/App Store purchase being made and the payment going through.

If I change my payment information after making a purchase, but before I am billed, which one will be used?
After trying it; it seems that the payment is taken from the card set up at the time of purchase.