I’ve submitted my debit card information correctly to chamge my payment method, i want to buy application on app store but i am having issue to change my payment method. please help me

Try a different card, preferably a credit card (though you could also try other debit cards).

For a card to have a chance of being accepted it needs to be registered to the same name and address (including format and spacing etc) that you have on your iTunes account, and have been issued by a bank in the country where you are (and therefore the country which is on your iTunes account).

What's the issue ? If you are getting a 'declined' message then it's possibly due to it being a debit card, not all seem to still work with iTunes.