Contact EASA who are compelled to bring it to the attention of the Greek authorities and then make sure you sought legal advice.
EASA is already made aware of this school and the more people who complains, the better for results.
It is unacceptable to blackmail and limit your training especially when it is hero's error!
Meanwhile, the boss is enjoying the high life on your and other unhappy students money!
These kind of greed need to be targetted an stopped!
So try what every angle. It may or may not get you somewhere but no harm in trying every option.
I have inboxed you the details who personally replied to me.