Was an Optus customer a while back.
Have changed some things like my email address since then. But not my credit card.
Just got a fairly obvious scam email saying my credit card had been charged with a substantial amount of money to pay for a McAfee subscription. The email address it was sent from was a gmail address. The contact number was a mobile. It told me I had 24 hours to contact them if I wanted to cancel.
Checked with my bank. No such charge.
But it does confirm Optus info is out there, info that wasn't in those 10,200 leaked ones, info about past customers, and its being used.
I don't understand how you have come to the assumption that this has to do with the Optus hack? The email had your credit card details written in it?