reset flexslider 2

I have a slider (flexslider2) that takes the data of a json which changes depending on a value that happened to the function. The slider is generated automatically. The problem is that when I want to change the json's data, calling the function again, the slider does not change. This is the code already solved.

function conv_bus(txtBus){
var parametros = {
    "txtBus":txtBus,
}

$.ajax ({
    data: parametros,
    url: "php/AgrApp/conv_bus.php",
    type: "POST",

beforeSend: function(){
    $("#proceso").html("<img src='img/cargando.gif' />"); //Cargo la web en el div
},  

success: function(data){

$("#proceso").html(""); //Cargo la web en el div
    objJsonConBus=JSON.parse(data);

    $("#lblSlider").html("<h4><span class='modal-title label label-default'> <span class='  glyphicon glyphicon-picture'></span> Carrusel de Convenios</span></h4>");
    var conv ='<div class="flexslider carousel">'+
     '<ul class="slides">';
    $.each(objJsonConBus, function(f, convenio){
        subDescuento = convenio.dsc_desc.substring(0, 52); //Estas funcion es para capar el campo descripción de descuento.
        conv += '<li>'+
        '<div data-name="'+convenio.name+'"data-desc="'+convenio.dsc_emp +'"data-des_desc="'+convenio.dsc_desc +'"data-dir="'+convenio.dir +' "data-toggle="modal"  data-target="#myModal" >'+
            '<center><img class="img-responsive " src="'+convenio.base64_png+'" />'+
            '<h5 CLASS="descuento ">'+subDescuento+'</h5></center></div>'+
        '</li>';
    });

    conv +=  '</ul>'+
    '</div>';


    $('#carrusel').append(conv); //Aqui le estoy asignando al div de convenios toda la informacion

    $('.flexslider').flexslider({ //Convoco al objeto 
        animation: "slide",
        animationLoop: true,
        itemWidth: 150,
        itemhight: 150,
        itemMargin: 20,
        pausePlay: true,
        mousewheel: true,
        slideshowSpeed: "2500",
    });


    }   
});

}

Html

<div id="lblSlider"></div> <!--- Esto es un label que indica el nombre del slider---->
        <div id= "divSlider"  class=" col-md-12 row-no-padding">    
            <div id="container" >
               <div id="main" role="main">
                  <section class="slider">


                            <div id="carrusel"></div> <!---Aqui se pinta el slider de imagenes------->


                  </section>
               </div>
            </div>
        </div>