so first was it a contracted handset
second did you have mobile insurance through Optus.
if yes to first but no to second as suggested buy another handset and continue paying your handset repayment. If you had insurance see this page for details.
If you can't get to a store or you're living in a rural area, call us to organise a replacement SIM card.
Alternatively, you can buy a new device online.
Important: if you choose to buy a second-hand device, check the IMEI number to ensure it hasn't been barred or blocked. Optus can only unblock a device with the original Account Holder's permission.