How to pay my bill through my bank account?

For info we are fellow users here on these forums, you're not talking to iTunes Support nor Apple

You can use one of the payment methods that show on your account. On your computer's iTunes you should be able to edit your payment info by going into the Store > View Account menu option and logging into your account, and on your account's details page there should be a payment link. If you are doing it on your iOad then tap on your id in Settings > iTunes & App Store and the tap 'View Apple ID' on the popup and log into your account - that should also give you a payments link on your account's page.

Changing payment info : http://support.apple.com/kb/HT1918

If you don't have any of the payment methods listed on your account then are iTunes gift cards available in your country (they are not available in all and they are country-specific, they can only be used in their country of issue) ? If they are then you could potentially use them as your payment method.

There isn't a bank account option, you will need to use of the options that is listed on that screen e.g. visa credit card (debit cards are also accepted in some countries), MasterCard, possibly Maestro and/or PayPal (I think PayPal is US only, but I think that can be linked to a bank account) - if iTunes gift cards are available in your country (they are not available in all and the cards are country-specific) then you might also be able to use them as you payment method.