I had previously booked a flight for my wife and I from Hong Kong to Sydney - QK*YFY...

I had previously booked a flight for my wife and I from Hong Kong to Sydney - QK*YFY. The flight was cancelled because of the worldwide Covid problem. We were not able to get a refund, as the tickets I purchased on the internet were non refundable. If it was not for the Covid issue, we would have been able to sail to Hong Kong and then return by air to Sydney. I find that I am now $*,***.** out of pocket with no refund being offered, but we have been offered the opportunity to use the credit on future travel. I have previously tried to write by e-mail (I am very deaf and cannot discuss things on the phone), but I have asked if I can use the funds for air travel in ****. We have booked a cruise leaving Darwin **th March, so we will need to fly from Sydney to Darwin **th or **th March ****. We would also be looking at flying from Broome to Perth **th or **th March ****. We would then need to return from Perth to Sydney *th or *th April ****. Are we able to use our credits towards the cost of these flights? I ask this as the flights are in March * April **** - ** months away. I would appreciate some sort of response as to the possibility of using my credit towards these flights. I would appreciate your word.*Thanking you in anticipation . David