I have book two one ways in August for an Aegean flight to Santorini from Athens and the prices (as well as the fare class) have come down considerably. I emailed (as i can't find anything on their website) to see if I could change (which I can according to the fare code) and haven't heard anything for three days. I'm here in Boston, wrote in English and do not speak greek.
The Fare Rules on Aegean website state "PHYSICAL PRESENCE IS REQUIRED" for changes or refunds to Internet Economy Class Fares within GREECE. They also list penalties "within 24 hours before departure". If it's an X/V/U/T fare it appears that you will get nothing back. It seems you will need to visit Aegean perhaps at the Athens airport to get refunds or exchange.
You probably need to call them and ask about your options. Don't worry about speaking Greek, they can respond to you in English. I just have no clue if the response will be helpful. Let us know.
This summer will be our first Aegean flight after years of ferry boats and Olympic flights.
Programs: A3*Gold, SPG Plat, HyattDiamond, MarriottPP, LHW exAccess, ICI, Raffles Amb, NW PE MM, TWA Gold MM
Once I had to rebook an island to ATH flight in business class to later in the same day after I had missed my flight because the hotel failed to do my wake up call. My ticket was part of a TATL complex trip, not on A3 stock and ticketed by AmEx. When I reached my TA by phone, she was able to make the changes instantly and efficiently, at no additional fare. Check in at the airport was efficient and drama free, with no additional time needed. Except for the hotel, it was a good experience.