My card is blocked in Apple ID

What do you mean by the card is blocked? Why do you have to unlock it? Can you add a new card and then remove the old card?

If necessary, contact iTunes Support for assistance. See the Apple Support articles below for contact information.   

iTunes Support – world wide   -

Apple Support schedule phone call     -

Billings and Subscriptions   -

Apple on Twitter

You should have the option to remove the card, once removed add it back in or add another card before removing the blocked one.