private void Btn_Demandar_Click(object sender, RoutedEventArgs e)
        {
            MessageBoxResult messageBoxResult = System.Windows.MessageBox.Show("¿Adquirir servicio? ", "Confirmar Adquisición", System.Windows.MessageBoxButton.YesNo);

            if (messageBoxResult == MessageBoxResult.Yes)
            {
                User u = UserManagement.GetInstance().CurrentUser;
                try
                {
                    AdminMgm.NewPayment(u, ser, PaymentType.Direct);
                }
                catch (Exception ex)
                {
                    MessageBox.Show("Compruebe su saldo en tokens o hable con un administrador de TimeBank\n \n Detalle: " + ex.Message, "Alerta: SERVICIO NO ADQUIRIDO", MessageBoxButton.OK, MessageBoxImage.Information);;
                }
            }
        }
        public bool PayService(User user, Service service)
        {
            try
            {
                IEnumerable <PaymentType> payMethods = _adminMgm.GetPayMethods();
                foreach (PaymentType t in payMethods)
                {
                    Console.WriteLine(t.ToString());
                }
                Console.WriteLine("CHOOSE PAY METHOD");
                string p = Console.ReadLine();

                _adminMgm.NewPayment(user, service, (PaymentType)int.Parse(p));
                return(true);
            }
            catch (Exception e)
            {
                Console.WriteLine("PAYMENT PROCESS NOT FINISHED : " + e.Message);
                throw e;
            }
        }