how do I run a search and limit it to one departmental store?

Hello,
We currently have bronze and are trying your Product data API. We are trying to limit search to Target store only, and are using the below json. but we are getting : "errors": ["Providing merchants is not permitted."]

{
"query": "name:(Prepaid Calypso)",
"format": "json",
"download": false,
"num_records": 1,
"merchants":[{"name": "Target"}]
}

The above works without the "merchants" element. Please advise