It is a return request.

If it is FBM just accept the return request then if the item returned is wrong or they have used an incorrect return reason you can file a SAFE-T claim.

If if is FBA nothing you can do they will just accept the return. They may have been sent the wrong item as it does happen on FBA

These kind of incorrect returns happen a fair amount. Sometimes buyers are mistaken other times it is deliberate to get a free return.