angular.js - set templateUrl dynamically by language (app.config stateprovider)

I'm developing a mobile app using Ionic framework and I have a big problem to handle the multilanguage functionality for help page.

I have 2 languages (en + de) and I want to load help_en.html or help_de.html depending on the language.

I have set in the main controller the default language and the changeLanguage function which will set the lang in $cookies.language and it's working;

1.View:

    <a ng-href="#/help" > 

2.MainCtrl -change language function:

    $scope.changeLanguage = function(lang) {
      $scope.translation=translationService.getTranslation($scope, lang);
      $cookies.lang=lang;
    };

3.The config from app.js looks something like that :

    var myApp = angular.module('MyPetApp', ['ionic', 'config', 'MyApp.controllers', 'ngCordova', 'ngResource', 'ngCookies']);

  myApp.config(function($stateProvider, $urlRouterProvider) {
    var $cookies;
    angular.injector(['ngCookies']).invoke(function(_$cookies_) {
      $cookies = _$cookies_;
    });
    if ($cookies.language==undefined){
      $cookies.language = 'en'
    }

    $stateProvider
      .state('default', {
        url: "/",
        templateUrl: "templates/default.html"
     })

    .state('help', {
        url: '/help', 
        templateUrl: function (){
            return 'templates/help_'+$cookies.lang+'.html'
        }
    })
      $urlRouterProvider.otherwise('/');
  });

This is working in chrome but on mobile will stay all the time on "en" language even I change the value from $cookies.language to "de".

What can I do to get this job done? Any ideea ? I really appreciate any help

Thanks