Refund request API call returns error 400

[Iván García]

I'm trying to develop a process that finally calls to the refund request endpoint, but all the test I have tried failed. 

I always get the error: 

{
    "status_code": 400,
    "error_description": "You should provide an event_id or antiquity_days",
    "error": "ARGUMENTS_ERROR"
}

I'm testing the next POST request.

{
 "from_email":"test@email.com",
 "from_name" : "Name",
 "items" : [{
 "order_id":"555656565",
 "event_id":"43534534534",
 "item_type":"order",
 "quantity_requested" : "1",
 "amount_requested": {
 "currency": "USD",
    "value": 0,
    "display": "$0"
 }
 }],
 "message":"Refund requested by duplicated order",
 "reason": "duplicate_order"
}

What am I doing wrong? Could someone share with me a request example that works??

Thanks