Unobtainable contacts with Ethiopian air

Good day I have scoured the internet for new emails or contacts for Ethiopian Air and sent emails to many places found on their sites which just bounce right back. I have phoned their telephone lines and just been put on hold with automated voices. I have been to their online site, There is nowhere where one is advised what to do with the vouchers issued last year for travel to Greece. At the moment, we can't travel there anyway. So what to we do or how do we het our money back for these 2 tickets that I have paid for already. It is very frustrating not being able to contact somebody! Please Ethiopian Air. I thought that you were such an up and coming airline. I was really looking forward to using your services Now you are just not contactable. HELP PLEASE.