My credit card was blocked by Apple

You can contact Apple whichever way you want, and they're still not going to unblock your card. Twitter is the same people as chat and phone and email support. They're all trained the same and follow the same policies. You've already contacted Apple and been given a solution; just because you disagree with it, it does not change that the fact is you must use a different card to use the iTunes and App Stores. Future contact with Apple will reiterate this, and the harder you push the more they are likely to be stricter and less willing to work with you.

This is what happens when you report that your account or card has been used fraudulently-- Apple is trying to help protect you from future fraud.

If you don't want this to happen, don't demand refunds for stuff you "didn't purchase".

Just an FYI, if you don't read the fine print that doesn't exempt you from payment; you are still technically legally bound by the agreement even if you believe/state you were duped into the purchase by a third party. That's not Apple's fault and they're not obligated to refund you under any circumstance. They did so as good will. Accept the consequences of your actions (i.e. not reading / fully understanding what you were downloading and then reporting fraud--which is illegal in most places, by the way, so you better be certain that your card actually was used fraudulently) and use a different card, buy iTunes Store credit, or use PayPal.

If you don't want to contact them through the standard ways you can use https://twitter.com/AppleSupport

You will have to ask Apple why they can't unblock the card, we are fellow users.

By Apple I mean Apple/iTunes Support. You can contact them via multiply methods : http://www.apple.com/support/itunes/ww , iTunes Store - Contact Us - Apple Support etc.

You would have to ask Apple why, we are fellow users.