How to make a Phone Call from a Windows Phone 8.1 App ?

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices.WindowsRuntime;
using Windows.ApplicationModel.Calls;
using Windows.Foundation;
using Windows.Foundation.Collections;
using Windows.UI.Xaml;
using Windows.UI.Xaml.Controls;
using Windows.UI.Xaml.Controls.Primitives;
using Windows.UI.Xaml.Data;
using Windows.UI.Xaml.Input;
using Windows.UI.Xaml.Media;
using Windows.UI.Xaml.Navigation;
namespace WP81ACXAMLApp
{
    public sealed partial class MainPage : Page
    {
        public MainPage()
        {
            this.InitializeComponent();

            this.NavigationCacheMode = NavigationCacheMode.Required;

        }
        private void Button_Click(object sender, RoutedEventArgs e)
        {
            // How to make phone call in Windows Phone 8.1 Apps
            PhoneCallManager.ShowPhoneCallUI("Abundantcode Phone Number here", "Abundantcode");
        }
    }
}