What a pain !
I thought you might be able to use Bank@Post, but alas a quick search says no . . .
The options are in the AI reply below . . .
(Note - There COULD be a caveat, and it is mentioned below, regarding Suncorp no longer accepting PERSONAL cheques, so they might still take cheques from business / corporations ??)
No, you can no longer deposit personal cheques into a Suncorp account at Bank@Post outlets, Suncorp branches, or ATMs, as Suncorp stopped all personal cheque deposits on February 14, 2025. You will need to arrange for the cheque issuer to provide a direct deposit, use another banking method, or deposit the cheque at one of the major banks that still accept cheques before the complete phase-out of cheques by 2030.
I guess the last option "deposit the cheque at one of the major banks that still accept cheques" is if you also have a bank account with another such bank.
Your idea to cancel the cheque and direct deposit is the best option, and if any future amounts are forthcoming, this can be nominated as the normal refund method moving forward.
An AGL rep might be along to say they have messaged you.