Qatar Airways complaint: Our destination has been changed.

My complaint:

On 15122021 my wife and myself booked flights to Perth Australia. These flights were paid for and ed by Qatar Airways on 15122021.
The flights booking is PPDPIU,
Elizabeth McCormack Ticket 157-2313506943
Michael McCormack Ticket 157-2313506944
The flights are booked for outbound from Dublin 19022022 to Doha and on to Perth.
The return is 16052022 back from Perth to Doha and into Dublin.
On 05022022 I received an email from Qatar Airways to inform me of a change to one of the flights on the itinerary, this was not major and we could accept that
However on 07022022 I received a further email to inform me that our destination was now being changed from Perth to Brisbane while the return flight still departed from Perth. The letter also stated that we would have to make our own arrangements to get to our destination which was Perth. The email gave an option of cancelling these flights altogether.
I phoned the Airlines Dublin office to express my concern and to reiterate that our destination was Perth, this is where our family live and we have been waiting for some years to visit them and for the first time see our grandchildren who are over 2 years old now.
I was told that the alternative would be to cancel the flights and get a refunds. I explained that I did not want to cancel our flights and that my one issue was that Qatar should get us to our booked destination which was Perth.
The Qatar representative said that at present she could not give us an alternative flight date but when one came available that we would be informed of this. I reiterated that I did not want to cancel our flights even if we had a changed departure date, that we would still need the return date as booked and ed.
The representative agreed that the flights would not be cancelled.
We have been shocked to receive on 09022022 notification that our flights have been cancelled and with no indication or effort to inform us of when alternative flights would be available.
This is causing great concern and upset among our family in Ireland and in Perth. I am making this complaint through Complain.biz but I have been in contact with the Irish Travel Regulator for advice as to how I should proceed with and direct my complaint.
I believe it is wrong of Qatar, firstly to redirect us to a city which is not our ed destination and to make no arrangements to transit us onwards to Perth, and secondly I believe that it is wrong for Qatar to cancel our flights when there are clearly alternative routes available to them to get us to our destination.
We simply want that we are treated fairly and are given what we paid for. To fly from Dublin to Perth and back.

Yours sincerely,
Michael McCormack

Suggested solution:

I believe that it is well within the scope of Qatar Airways to fly us from Dublin to Perth and back without the proposal of abandoning us in another city.
I want Qatar to fulfil their part of our contract.