Welcome to the forum @leem,
That is a shocker, and I moved your post into this older topic about the same issues, although with a different flavour.
@Phloesmum anecdotally noted in 2018 that RACV has problems doing direct debits and it seems they have not gotten any better, and possibly even worse as your experience shows.
I recommend you lodge a formal written (real mail or email) complaint to RACV in a dispassionate factual manner and see how they respond. You will need to start by ringing them on 13 72 28 and asking for the appropriate email or postal address to start, and do not accept being fobbed off. As you discovered talking to RACV by phone is nothing but idle chit chat while written correspondence can be evidence.
In my experience RACV has been a fail in responding to queries, where they summarily ignore that which they are not interested in responding to. Following on from approaching RACV you can also contact AFCA with your complaint.
Since RACV is highlighted from time to time, please let us know how you proceed and any outcome.