Failed Refund

Was charged 690 euro at the airport due to a mistake by the airline booking staff. Later they sent me an email admitting fault and promising reimbur*****t. Its been over 2 months and I still haven't been reimbursed. I am at my wits end. It is impossible to contact the department of the company via phone call or email; the only way to get hold of them is via an obscure form. I will never fly again with this airline until I am reimbursed.