But they knew the cards were used for btc trades from the beginning. But suddenly this was a "problem".
They also didnt unblock or withdrawl the balance after all docs were provided they asked for. For me thats clearly scam!
Exactly what happened to me with an old Bitcurex Card, issued by BZWBK. The card was sold by a Polish exchange, namely Bitcurex, which signed an agreement with the bank, so they were 100% aware that card would be used in connection with bitcoin trading. One year later the bank bastards changed their policy as well as the card's TOS, and they applied it even to cards that had already been issued! Then my card got blocked and I could get my balance back only thanks to Bitcurex' guys, who went to a bank's branch in Poland and demanded full buyout.
There are many ways to become money back, lawyers can build the help
Sure, suppose you have some 100€ left on a blocked card, you would give your lawyer twice your balance just to file a lawsuit