Adwords Call Forwarding in Google Tag Manager

Get your conversion code from adwords.

Define a CSS selector for the HTML element that contains the phone number to be converted.

Create a new tag in GTM
Select a tag configuration of Custom HTML <>
Paste the JS conversion code into the textarea.
Define a trigger of All Pages.

Just before the closing tag, paste the number replacement script:

//Change the values in this section to customize for your implementation.

//Replace with business's phone number EXACTLY as it appears on the website.
 var business_number = "(555) 555-5555";

//Replace with business's phone number without spaces or symbols.
 var business_number_unformatted = "5555555555";

//Replace this value with the CSS selector for the phone number's element.
 var business_number_identifier = "h2.site-description";

//End customization section

var callback = function(formatted_number, unformatted_number) {
 var numberElement = document.querySelector(business_number_identifier);
 var numberString = numberElement.innerHTML;
 numberString = numberString.replace(business_number,formatted_number);
 numberElement.innerHTML = numberString;
 };

//The line of code below is for testing with GTM's debug mode.
 //It replaces the business phone number with a testing number (666-666-6666).
 window.onload = callback('666-666-6666', business_number_unformatted);

//This code executes everything. When you're done testing and you're ready to publish the
 //GTM container, place '//' in front of the code above, and remove the '//' below.
 //window.onload = _googWcmGet(callback, business_number);

//Change the values in this section to customize for your implementation.

//Replace with business's phone number EXACTLY as it appears on the website.

var business_number = "(555) 555-5555";

//Replace with business's phone number without spaces or symbols.

var business_number_unformatted = "5555555555";

//Replace this value with the CSS selector for the phone number's element.

var business_number_identifier = "h2.site-description";

//End customization section

var callback = function(formatted_number, unformatted_number) {

var numberElement = document.querySelector(business_number_identifier);

var numberString = numberElement.innerHTML;

numberString = numberString.replace(business_number,formatted_number);

numberElement.innerHTML = numberString;

};

//The line of code below is for testing with GTM's debug mode.

//It replaces the business phone number with a testing number (666-666-6666).

window.onload = callback('666-666-6666', business_number_unformatted);

//This code executes everything. When you're done testing and you're ready to publish the

//GTM container, place '//' in front of the code above, and remove the '//' below.

//window.onload = _googWcmGet(callback, business_number);

Save the tag and select GTM’s Preview and Debug mode. Then test the website. If the tag is configured successfully, the phone number should be the debug number:666-666-6666.

Now disable the debug number and activate the Google number:

Comment this: 
 //window.onload = callback('666-666-6666', business_number_unformatted);

Uncomment this:
 window.onload = _googWcmGet(callback, business_number);

Comment this:

//window.onload = callback('666-666-6666', business_number_unformatted);

Uncomment this:

window.onload = _googWcmGet(callback, business_number);

Publish Tag Manager and conclude the task.