how can i tell itunes to deduct fee of app from my debit???

i have brought app for iphone yesterday by using debit card . The problem is i want to close my bank account which i use that debit card .i went to bank yesterday and the bank said it's still pending of purchase itunes stuff .at first i thought it gonna be settled the same time i brought but today it's still pending in my account. how can i tell them(itunes) to deduct it from my debit coz i gonna leave the town where this bank located on friday and never come back. I cant wait

thank you