       <f:selectItem itemLabel="Select Payment"></f:selectItem>
                                                <f:selectItems value="#{enumController.paymentMethodsForPharmacyBilling}" />
                                                <p:ajax 
                                                    process="cmbPs" 
                                                    listener="#{pharmacyPreSettleController.checkAndUpdateBalance()}"
                                                    update="panelPaymentDetails