Web Forms :: Label Does Not Show When Set Visible True

I have 3  image button  in my page 

1- Imgabout_Click  
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
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 until now every thing work correctly but when i click on  imgcontact_Click again it should lblcall.Visible = true again but it didn't

I mean 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?

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";

[Code] ....