api for voip integration need agent phone number

[mail4arunkr@gmail.com]

I want to call an api from phone button click and i have managed it successfully. But I want to take the agent / assignedUser phone number also to pass for sending with api. Kindly help on this. I have done as follows,
client/res/templates/fields/phone/detail.tpl
i have changed <a data-phone-number="{{valueForLink}}" id="custom_api_call" data-action="api_call">

and in html/main.html

<script>

$(document).on("click","#custom_api_call",f unction() {

try{
var phone = $(this).attr("data-phone-number");
and then call api

Somehow i want to take the phone number of the assighnd user and to make it available on the script page abovementioned. I am doing this to avoid voip integration and handle it via API, kindly help regarding this
Thanks
Arun
919496381412