the correspondence has probably been forwarded to CASA.
i. should have added- so they will write the Ministers response. They will then forward that back to the Minister for approval through the Department of transport who will do their own assessment of CASAs response.
At at this point the Minister is not really involved - which is as it should be in Westminster style government. The Minister takes “advice” from his Department which is why his letter will say words to the effect: “I am advised that...... “.
To effect any change, assuming CASA will not give you what you believe you are entitled to, you will need to make a case strong enough that the Department of Transport takes action to make CASA do something or failing that, that the Minister is galvanised enough to ask his department to do something which may not be possible under the Aviation Act. Then the Minister needs to go to Parliament.
There is a settled hierarchy of actions - the minister can’t just pull a decision out of thin air. Good luck, get legal advice and don’t do anything rash.