How do u unblock a debit card from your apple account

How is it 'blocked' ? What happens when you try to use it ? If you are getting an error message what does it say ? If you are getting a 'declined' message it might be because it's a debit card, not all seem to still be accepted by iTunes - so if it is being declined you might not be able to use it.

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).