Experience Oz Tracking Order Status

My mother bought me and my partner 2 x tickets for a river cruise on the Yarra. Finally got around to redeeming them after all the crap with the pandemic. Then on the day of the cruise my partner has a heavy cold so asks me to rebook for another day. Called Experience Oz and they would only rebook if we (a) paid them $60 a head on top of the already purchased tickets or (b) provide a doctor's certificate! Told them I'm not willing to pay more and it's plainly ridiculous for me to tell my partner to get out of bed and head to the doctors to get confirmation of a head cold. But they wouldn't budge. It's policy, I was told. What a terrible way to treat people.