Based on the Greek Law of EOT,
(Greek organisation of Tourism), article 3:

All the deposit will immediately be paid back for
cancellations made more than 21 days before arrival.
This applies for all reservations made from Internet,
telefax, telephone etc.

For cancellations made later than 21 days before
arrival, or in case of no show, 50% of the cost for
not used days will be charged.