I live in the US and am moving back to Aus shortly. As the chat is disabled for COVID-19 I can't chat for someone to assist with this, and also can't call from overseas so this is my last resort.
Back when I used to live in Aus I was with Optus for many years, and I am looking to get the number back.
Is someone from Optus able to assist me with this?
Optus can not help you through this public forum.
If you have been without that number for more then 6 month you will almost certainly be out of luck and the number would have been returned to the pool for reallocation.