Why did my return item come back to me?

I live in Australia, Melbourne

bought a camera recently from EBay it was from a local seller in QLD, however the camera didn’t work so I requested a refund, sent it into the post office, had the label scanned and printed there, then it was all done.

All of a sudden I had gotten the same package I sent in at my front door 8 days later, I did not get any refund yet.

At this point what am I meant to do?

I’ve contacted the seller and they said “they don’t know what business I have with the shipping company” which is Australia Post, so it’s assumed they don’t know what is going on as well.

The tracking details show it arrived in Queensland but it’s at my front door…? I’m super confused right now….