Everytime i try to update my billing info even if my card info is correct it would show that its declined or the payment failure.

If it's a debit card that might be why, not all seem to still be accepted by iTunes. Or if it's a prepaid card. Try a different card (preferably a credit card).

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).