{
  "startDate": "2019-09-18T00:00:00-05:00",
  "endDate": "2019-09-18T23:59:59-05:00",
  "locationId": [
    106
  ]
}

  Dim apiCall As IRestDriver
  Set apiCall = RESTDriver.Create(URL, REQUEST_GET_CUSTOMERS, SITE_ID, API_KEY)

  With apiCall
    .RequestHeader("Content-Type") = "application/x-www-form-urlencoded"
    .bodyParameter("response_type") = "xml"

Private Property Let IRestDriver_RequestHeader(ByVal key As String, ByVal Value As String)
  this.requestHeaders.Add key, Value
End Property

Private Property Let IRestDriver_bodyParameter(ByVal key As String, ByVal Value As String)
  this.bodyParameters.Add key, Value
End Property

Private Type TInfo
  requestHeaders As Scripting.Dictionary
  bodyParameters As Scripting.Dictionary
End Type

Private this As TInfo
Implements IRestDriver

  Set this.requestHeaders = New Scripting.Dictionary
  Set this.bodyParameters = New Scripting.Dictionary

POST /Appointments/GetAppointments?Authorization:Basic=<snip>:<snip>&amp; response_type=xml&amp; location=106&amp; start_date=20190924&amp; end_date=20190924 HTTP/1.1
Host: ws.appointment-plus.com
Content-Type: text/plain,multipart/form-data; boundary=--------------------------031106076178821554951247
Authorization: Basic <snip>
User-Agent: PostmanRuntime/7.17.1
Accept: */*
Cache-Control: no-cache
Postman-Token: 4f2fe7a8-88e4-4c78-b473-7b516a4947b9,bce49aaa-1391-4f69-b010-8cd584c157e7
Host: ws.appointment-plus.com

var client = new RestClient("https://ws.appointment-plus.com/Appointments/GetAppointments?Authorization:Basic=<snip>:<snip>&response_type=xml&location=106&start_date=20190924&end_date=20190924");
var request = new RestRequest(Method.POST);
request.AddHeader("cache-control", "no-cache");
request.AddHeader("Connection", "keep-alive");
request.AddHeader("Content-Length", "284");
request.AddHeader("Cookie", "PHPSESSID=mrnhsnke5m0t7ic3un502vjg21");
request.AddHeader("Accept-Encoding", "gzip, deflate");