Dynamic image replacement through CallRail Phone Call Tracking plugin

Hi,
I want to dynamically swap an image that contains a phone number.
I followed steps given (http://www.callrail.com/docs/web-integration/dynamic-number-insertion/images/ ) but images not swapped.

I installed plugin CallRail Phone Call Tracking and set the api key through call rail account and paste the javascript code in the footer of the page.

I saved the image of destination number tollfree.png in the image folder on the webserver wiith your prescribed naming convention i.e tollfree.8005676745.png

Then I saved the tracking numbers images with the same naming convention i.e tollfree.8889975025.png (8889975025 is tracking no. ) in the same image folder on the webserver.

Then I replaced the references i.e url(“images/TollFreeOverlay.8005676745.png”) to url(“images/TollFreeOverlay.8005676745.png”)

Earlier code :
<div id=”main”><div id=”tollfreeoverlay” ></div>
and given the reference through css
#tollfreeoverlay {
background: url(“images/TollFreeOverlay.8005676745.png”) no-repeat scroll 0px 0px transparent;
height: 32px;
position: absolute;
right: -120px;
top: -310px;
width: 540px;
z-index: 99;
}

After that i created new class in same div tag.. eg.
<div id=”tollfreeoverlay” class=”tollfree_temp”></div>
css will be
.tollfree_temp {
background: url(“images/TollFreeOverlay.8005676745.png”) no-repeat scroll 0px 0px transparent;
}

When i search my website through google search image didn’t swap bt in call rail account it maintain the log that i search through google organic.
888-997-4982 6 minutes ago Google Organic

I want to swap the images as per callrail logs.So plz suggest the solution for the same
Thank you