Send them a message here, on e-mail or post a dedicated thread, and give them a 7 day hard deadline.

After that deadline has passed and if you have not received your coins, file an official complaint with your local french embassy, any trade organisation that's suitable, and send a letter to their banking partner, +file a complaint with the police in their jurisdiction. Even if that probably would not help a single bit, if an entity receives some complaints, it might look into it, and besides it's bad PR, which they rightfully deserve to receive if they don't handle the case properly. The waiting time has been long enough, it's time to bring out real consequences.

And it's never about the amount, but always about the principle.