Unable to re-book tickets on hold

During the time their flights were grounded in March 2022 I informed Kulula via multiple emails from the 14th of March that I booked flights on another airline for the below flights. Since then I received two emails from different agents that I can re-book these flights within 6 months, but everytime my wife phones to re-book the ticket for her daughter she is told that the ticket is not active. We would have received call backs from agents, but no one ever phones back.