Auto-authorised return

Hi I’m a new FBM seller, why is there Auto-authorised return? I got a return/refund request, the reason is “wrong item sent”. Postage label is “Returnless refund”. I don’t even have option to refund or not.

I remember I shipped the correct item to that buyer just the other day. I then messaged the buyer about the issue and asked for photo, she then said the item never arrived, we haven’t even finished the communication, I got the email saying Amazon has initiated refund to the buyer. I checked the case and its close and refunded to buyer already.

There are some cases that I have option to issue refund or not, but what will be “auto-refunded” to buyer? Where can we set or how do we avoid? Thanks.