Angular Inject Service in angular.config

In my app.config i need to retrieve a value from a service but i have an error message : UserServiceProvider.getUser is not a function. The goal is to allow the user to access some pages only if he is a part of a list.

Here's my service code :

var app =  angular.module('myApp');
  app.service('UserService', '$http', '$q', function(){
   userService.getUser = function () {
        var deferred = $q.defer();
        return $http.get(userUrl + "getUserName")
             .success(function (data) {
                 deferred.resolve(userService.userName = data);
                 console.log(data);
                 //alert('Success loading user');
             }).error(function (error) {
                 deferred.reject(error);
                 //alert('Error loading user' + error.message);
             })
        return deferred.promise;
    }
    return userService;
  });

My config :

  app.config(function(UserServiceProvider){
     UserServiceProvider.getUser()
      .then(function (data) {
          console.log(UserServiceProvider.userName);
      });
  });