firstly, this is not a good thing to happen to anyone.  Do as padi has suggested. 

Secondly, we would need more details in order to provide more advice than what wise padi has given.

- how was the fraud perpetrated?

- does the payment show on your CC statement?

- how did you find out about the fraud?  Was it through a phone call, text message or email?

I got an unsolicited phone call once where the caller told me my credit card had been used overnight on an $880 eBay purchase in the USA.  In order to find out more about the transaction the caller said I'd have to verify my identity and card details.  I asked them which card had been used, as I have a few, and they said for privacy reasons they couldn't tell me until I verified my identity.  I told them to let the transaction go through ... at this point they hanged up on me.

There was no transaction.  They were phishing for identity information.  Had I given them identity and/or card information I would have been scammed.

It isn't eBay's fault when people have been tricked into giving identity/card information to a cold caller and are subsequently defrauded on eBay.

Not saying this is how it happened in your case, just warning others about unsolicited cold callers.

It sounds like you've been scammed.

Did the payment go to EBAY COMMERCE AUSTRALIA PTY LTD  or somewhere else ?

It's very doubtful if eBay will help you if it was a scam, a chargeback through your credit card might be your only hope.