C.O.D. means 2 things.

1. Cash on delivery if you are going to deliver the item for the buyer.

2. COD being a service Aust Post offers. They deliver and pick up the cash, then you pick up the cash from Aust Post and pay an expensive fee.

So as stated don't offer it unless you are delivering the item yourself. And make it clear in the listing it is delivery from you only.

Offer C.O.P.U. (cash on pick up) if that is an option you want to provide.