ASP.Net Label does not show when set Visible true

hi

i have 3  imagebutton  in my page 

1-Imgabout_Click     and    2- Imgpro_Click   3-imgcontact_Click

according to code when i click each of these image button some label visibility be true or false i don't have any problem with  1-Imgabout_Click and  2- Imgpro_Click  there is problem with 3-imgcontact_Click

when i click on  imgcontact_Click   it lblcall.Visible = true;  and i can see lblcall(this is label) in my page after that i click on  Imgpro_Click   or  -Imgabout_Click    when i click these 2 image button   lblcall.Visible = false   untill now every thing work correctly but when i click on  imgcontact_Click  again    it should lblcall.Visible = true again but it didn't

i means when i click on this image button i can't see  lblcall in my page i think it didn't do  lblcall.Visible = true    it happened when i click this image button for second time why?

thanks

 protected void Imgabout_Click(object sender, ImageClickEventArgs e)
    {
        Imgabout.ImageUrl = "~/image/aboutus.png";
        Imgapro.ImageUrl = "~/image/imgpro1.png";
        imgarticle.ImageUrl = "~/image/imgpro1.png";
        imgcontact.ImageUrl = "~/image/imgpro1.png";
        lblabout.Visible = true;
 imgabout1.Visible = true;
        lblproduct.Visible=false;
        lblcall.Visible = false;
        imgpro.Visible = false;
        imgcall.Visible = false;
       
    }
    protected void Imgapro_Click(object sender, ImageClickEventArgs e)
    {
        
        Imgapro.ImageUrl = "~/image/imgpro.png";
        Imgabout.ImageUrl = "~/image/imgpro1.png";
        imgarticle.ImageUrl = "~/image/imgpro1.png";
        imgcontact.ImageUrl = "~/image/imgpro1.png";
       
        lblproduct.Visible = true;
        imgpro.Visible = true;
 lblabout.Visible = false;
        imgabout1.Visible = false;
        lblcall.Visible = false;
        imgcall.Visible = false;
    }
    protected void imgcontact_Click(object sender, ImageClickEventArgs e)
    {
        imgcontact.ImageUrl = "~/image/imgcons.png";
        Imgapro.ImageUrl = "~/image/imgpro1.png";
        Imgabout.ImageUrl = "~/image/imgpro1.png";
        imgarticle.ImageUrl = "~/image/imgpro1.png";

        lblcall.Visible = true;
       
        imgcall.Visible = true;
        lblabout.Visible = false;
   imgabout1.Visible = false;
        lblproduct.Visible = false;
        imgpro.Visible = false;
     
       

       
    }