Short answer: No, it can't be customized by you from wordpress.
You set up your app key and then at the bottom link to a
JS file. From there, the JS file dynamically creates a script element and loads more JavaScript from either clickdesk.com or appspot.com depending on the protocol you're viewing the page. The *additional* scripts loaded from one of those websites loads more scripts and dynamically creates div elements and children elements. Those scripts then append the elements to the body of your website.
The actual chat app is stored off site on those servers so there's nothing you can do to customize it with exception for maybe writing your own little JavaScript hack to replace innerHTML.
So I would request international support from the creators if you can or ask them if the support already exists. Weird restrictions like this is specifically why I stick to open source systems like
openfire with
Fastpath plugins installed (or alternatively
redfire+plugins).