AssigneeId field is ignored by the API

AssigneeId field is ignored by the API

I'm trying to create a ticket using the API. I am using the assigneeId field to assign the ticket to an agent. The call is accepted but it looks like the assigneeId field is ignored and the ticket is assigned to my own agent account. What am I doing wrong here?

Request:
  1. {
      "contactId": "296206000001692001",
      "secondaryContacts": [
        "296206000000107001"
      ],
      "subject": "Request | hardware",
      "dueDate": "2020-11-14T15:12:50.566Z",
      "departmentId": "296206000000006907",
      "description": "<div><h2>Hardware</h2><br>Laptop adapter<br><br><h2>Gebruiker</h2><br>Naam:<br>Functie: <br>Vestiging: <br><br><h2>Verantwoording</h2><br>Reden: Test</div>",
      "priority": "Low",
      "classification": "Request",
      "phone": "345",
      "category": "hardware",
      "email": "",
      "status": "Open",
      "channel": "VSA",
      "teamId": "296206000000088471",
      "assigneeId": "296206000000093187"
    }


Response
  1. {
      "modifiedTime": "2020-11-11T15:16:43.000Z",
      "subCategory": null,
      "statusType": "Open",
      "subject": "Request | hardware",
      "dueDate": "2020-11-13T15:16:43.000Z",
      "departmentId": "296206000000006907",
      "channel": "VSA",
      "onholdTime": null,
      "language": "Afrikaans",
      "source": {
        "appName": null,
        "extId": null,
        "permalink": null,
        "type": "SYSTEM",
        "appPhotoURL": null
      },
      "resolution": null,
      "sharedDepartments": [],
      "closedTime": null,
      "approvalCount": "0",
      "isTrashed": false,
      "createdTime": "2020-11-11T15:16:43.000Z",
      "id": "296206000007809001",
      "isResponseOverdue": false,
      "customerResponseTime": "2020-11-11T15:16:43.000Z",
      "productId": null,
      "contactId": "296206000001692001",
      "threadCount": "1",
      "secondaryContacts": [
        "296206000000107001"
      ],
      "priority": "Low",
      "classification": "Request",
      "commentCount": "0",
      "taskCount": "0",
      "accountId": null,
      "phone": "345",
      "webUrl": "",
      "isSpam": false,
      "status": "Open",
      "ticketNumber": "1464",
      "customFields": {
        "Office": null,
        "Host name": null,
        "Project/Client": null
      },
      "isArchived": false,
      "description": "<div><h2>Hardware</h2><br />Laptop adapter<br /><br /><h2>Gebruiker</h2><br />Naam:<br />Functie: <br />Vestiging: <br /><br /><h2>Verantwoording</h2><br />Reden: Test</div>",
      "timeEntryCount": "0",
      "channelRelatedInfo": null,
      "responseDueDate": null,
      "isDeleted": false,
      "modifiedBy": "296206000001037027",
      "email": null,
      "layoutDetails": {
        "id": "296206000000074011",
        "layoutName": "Computer Services"
      },
      "channelCode": null,
      "cf": {
        "cf_host_name": null,
        "cf_project_client": null,
        "cf_office": null
      },
      "layoutId": "296206000000074011",
      "assigneeId": "296206000001037027",
      "teamId": null,
      "attachmentCount": "0",
      "category": "hardware"
    }