That's really messed up.
Looking at their
trust page, there were plenty of others with similar issues, same goes for their
official thread in English, last few pages are basically (unaddressed) scam accusations. They locked that thread and limited themselves to Russian board. I'm very surprised they haven't yet received red trust from any DT member.
Regardless, you should send them a pm (if you haven't already) linking to this thread and give them a chance to respond. If they don't reply within few days, you can contact few DT members (ie
Vod and
cryptodevil and ask them to intervene by tagging them as scammers. That may not force them to release your funds but at least it will serve as a warning to others.
It's worth to note that in their T&C they claim to be operated by "ALWAYS EFFICIENT LLP", but the latest available accounts of that partnership (for the period to 31 July 2015) show no trading activity and entire assets of only £100.
But since it's UK registered LLP, you could also report them to
http://www.actionfraud.police.uk/ if you have no luck in getting your money back.