Itunes Store Billing Policy

I recently made a purchase for a Magazine Subscription through the Itunes store (Monday 04/26). Now four days later I am still waiting for it to hit the bank. I understand the store delays billing a couple of days because of small purchase amounts but this is a $23.00 purchase and it has been four days.
What is the maximum number of days the ITunes store will delay billing. And for a magazine subscription will it start on the date of purchase or when apple decides to bill me. I am already being asked to pay for issues I thought I had subscribed too !