$InsertQuery->bindColumn("lotNumber", "i", "item_number", "WA_DEFAULT");
$InsertQuery->bindColumn("duesAmtPaid", "i", "mc_gross", "WA_DEFAULT");
$InsertQuery->bindColumn("duesStatus", "s", "payment_status", "WA_DEFAULT");
should probably be:
$InsertQuery->bindColumn("lotNumber", "i", $_POST["item_number"], "WA_DEFAULT");
$InsertQuery->bindColumn("duesAmtPaid", "i", $_POST["mc_gross"], "WA_DEFAULT");
$InsertQuery->bindColumn("duesStatus", "s", $_POST["payment_status"], "WA_DEFAULT");