Kulula unfair

I purchased flights on Kulula in March to fly in Easter but could not be used because of the lockdown. I now wish to use it since they started flying again, only to be told that I can use it in Jan 2021. They have been unfair since the lockdown. They have refused a refund and now want to dictate when it can be used. Do the right thing Kulula and refund me cost of flight plus interest(since I can't fly when I want to). Tickets are of no use to me now.