function doesn't work after ajax succesfully sent data

Question

I have an Iframe with formwhi fields wich sent data to php file through ajax. If it was successful I close iframe (it is working) and create new one with another information. So question is: how to close the old iframe and open another one?

so here is ajax function that works but doesn't open a new iframe the function opening a new iframe work by it self but doesn't work in ajax. Where is a problem?

$.ajax({

        type: "POST",
        url: "sign.php",
        data: {name : name,
            data: canvasData
            },
        success: function () {

           //frame_activation(); //if it will be here it will open iframe inside the old one iframe. 
            alert('done');
            close_frame (); //closing frame with form
            $(body).html(argument[0]);
            //windows.top.frame_activation();
            frame_activation(); // does't work, doesn't open a new iframe

        }
    });

So the result is - the old iframe sent information and close it, but doesn't open a new iframe.

frame activation :

function frame_activation() {   
//document.getElementById('bg_frame').style.visibility = 'visible';
reg = document.createElement('iframe');
document.body.appendChild(reg);
reg.id = 'iframe';
reg.src = 'activate.html';
reg.style.width='600px';
reg.style.height='200px';
position_frame(reg);
reg.style.border='solid 5px #d4d4d4';
alert('here');
return false;
}

function to close iframe:

function close_frame () {
    parent.document.getElementById('bg_frame').style.visibility = 'hidden';
    var el = parent.document.getElementById('iframe');
    el.style.display='none';
    parent.document.body.removeChild(el);   
    return(false);  
}

function for creating first iframe with fields

function frame_reg() {  
    document.getElementById('bg_frame').style.visibility = 'visible';
    reg = document.createElement('iframe');
    document.body.appendChild(reg);
    reg.id = 'iframe';
    reg.src = 'frame.html';
    reg.style.width='640px';
    reg.style.height='400px';
    position_frame(reg);
    reg.style.border='solid 5px #d4d4d4';
    return false;
    }