Hi all,
Thanks for information!
I just called Qantas and the agent went to check the booking notes under my booking and I was informed that I was upgraded by the supervisor and henceforth, there's no downgrade involved and everything's fine.
Pretty much worried for the whole night that I will be downgraded to Economy due to the other agent's comment: there was a mistake in the booking etc.
On a side note, I even managed to change my domestic flight to half hour early without any problem
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