.net windows application

here is my code when am clicking link label didnt get that form but there showing error

Error 18 The best overloaded method match for 'OverdueSalesOrder.CallFromReminder(ReminderPopUp)' has some invalid arguments

Error 19 Argument 1: cannot convert from 'ile' to 'ReminderPopUp' ile.cs

private void lnklblReminderSalesdue_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)

{

try

{

frmOverdueSalesOrder frmoverdueSalesOrderObj = new frmOverdueSalesOrder();

frmOverdueSalesOrder open = Application.OpenForms["frmOverdueSalesOrder"] as frmOverdueSalesOrder;

if (open == null)

{

frmoverdueSalesOrderObj.MdiParent = formMDI.MDIObj;

frmoverdueSalesOrderObj.CallFromReminder(this);

}

else

{

open.Activate();

}

catch (Exception ex)

{

MessageBox.Show("pRPU:3" + ex.Message, "OpenMiracle", MessageBoxButtons.OK, MessageBoxIcon.Information);

}