Facebook messenger plugin is changing language

I inserted fb messenger plugin code in my website. Whenever I am clicking this plugin, the language changes. I am not using VPN. I also checked my IP address and it is located in my country. Even on mobile device, the language changes.

This helped me. I changed URL in SDK code the js.src parameter from:

js.src = 'https://connect.facebook.net/en_US/sdk/xfbml.customerchat.js';

To:

js.src = 'https://connect.facebook.net/en/sdk/xfbml.customerchat.js';

Notice that in the first URL there is /en_US/ and in the second there is only /en/. Now I have Facebook chat in english. Still better than random foreign language. I'm following this thread for better solution.

My code:

  <!-- Load Facebook SDK for JavaScript -->
  <div id="fb-root"></div>
  <script>
    window.fbAsyncInit = function() {
      FB.init({
        xfbml            : true,
        version          : 'v4.0'
      });
    };

    (function(d, s, id) {
    var js, fjs = d.getElementsByTagName(s)[0];
    if (d.getElementById(id)) return;
    js = d.createElement(s); js.id = id;
    js.src = 'https://connect.facebook.net/en/sdk/xfbml.customerchat.js';
    //js.src = 'https://connect.facebook.net/en_US/sdk/xfbml.customerchat.js';
    fjs.parentNode.insertBefore(js, fjs);
  }(document, 'script', 'facebook-jssdk'));</script>


  <!-- Your customer chat code -->

  <div class="fb-customerchat"
    attribution=setup_tool
    page_id="{Your page id}"
    theme_color="{Your theme color}"
    logged_in_greeting="Hi! How can we help you?"
    logged_out_greeting="Hi! How can we help you?">
  </div>