I'd say you've got pretty much zero chance at the moment. I've been disputing a refund with them for three months now. For the first two moths they totally ignored all communications. When they finally answered they quoted the new Greek law (passed in early May I believe) which allows them to issue vouchers. When I queried this and pointed out that national law does NOT override EU law (EU.261) they went quiet again and have since ignored my last three emails. Apparently the EU commission have recently reiterated that EU.261 is still valid and that they will take "steps" against the governments of countries that do not abide, but until that happens I think Aegean will stand their ground, or at least pretend to be deaf. From other posts (do a search) it seems the best way is via your credit card company, if that's what you used for payment, and that a lot of the card companies are indeed making refunds.