<p:commandButton 
                                            ajax="false"
                                            value="Refund Bill" 
                                            icon="fa fa-money-bill-wave"
                                            style="float: right"
                                            class="ui-button-warning" action="#{billSearch.refundOpdBill()}"
                                            onclick="if (!confirm('Are you sure you want to Refund This Bill ?'))
           