How to Send SMS using HTTP API in VB6 Code?

Private Sub Command1_Click()
 
     Dim DataToSend As String
     Dim objXML As Object
     Dim message As String
     Dim username As String
     Dim authKey As String
     Dim mobiles As String
     Dim sender As String
     Dim accusage As String
     Dim URL As String
 
 'Set these variables
 username = "UR_USER";
 
 authKey = "UR_KEY";
 
 mobiles  = "9974984500";
 
 'Sender ID,While using route4 sender id should be 6 characters long.
 sender = "SENDER"; 
 
 ' this url encode function may not work fully functional.
 message = URLEncode("Your Message")
 
 'Define route
 route = "default" 
 ' do not use https 
 URL = "http://temp.91bulksms.com/submitsms.jsp?" 
  
 Set objXML = CreateObject("Microsoft.XMLHTTP")
 objXML.Open "POST", URL , False
 objXML.setRequestHeader "Content-Type", "application/x-www-form-urlencoded"
     
 objXML.send "user=" + username +"&key=" + authKey + "&mobile=" + mobiles + "&message=" + message + "&senderid=" + sender + "&accusage=" + accusage
 
  If Len(objXML.responseText) > 0 Then
         MsgBox objXML.responseText
         
  End If
      
 End Sub
 
 Function URLEncode(ByVal Text As String) As String
     Dim i As Integer
     Dim acode As Integer
     Dim char As String
     
     URLEncode = Text
     
     For i = Len(URLEncode) To 1 Step -1
         acode = Asc(Mid$(URLEncode, i, 1))
         Select Case acode
             Case 48 To 57, 65 To 90, 97 To 122
                 ' don't touch alphanumeric chars
             Case 32
                 ' replace space with "+"
                 Mid$(URLEncode, i, 1) = "+"
             Case Else
                 ' replace punctuation chars with "%hex"
                 URLEncode = Left$(URLEncode, i - 1) & "%" & Hex$(acode) & Mid$ _
                     (URLEncode, i + 1)
         End Select
     Next
     
 End Function