I probably sound thick but why would using your card on AW get your card blocked??? I've used mine before to buy credits and it wasn't blocked. I don't get it.
I use my debit card for adult work, and never had any problems, and card has never been blocked, as for your credit card company; think all you need to do is tell them the truth, yes you did use your card to buy credits, so as for your card being blocked, don't think its any of there business
Don't forget there the data protection act, so even if you told them you have used your card to buy credits, tell them to unblock your card
It seems its the banks are the ones who think you are at risk of fraudulent transactions, not us; if you faced fraudulent transaction on aw, then surely that would be the end of aw