MySql Entity Framework example that produces duplicates

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using System.Data.Entity;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MySqlEFTest
{
    public class Company
    {
        public int Id { get; set; }
        public virtual ICollection<Customer> Customers { get; set; }
    }

    public class Customer
    {
        [Key]
        public int Id { get; set; }
        [StringLength(50)]
        public string Name { get; set; }
        public virtual Company Company { get; set; }
        [ForeignKey("Company")]
        public int CompanyId { get; set; }
        public virtual ICollection<Order> Orders { get; set; }
    }

    public class Order
    {
        [Key]
        public int Id { get; set; }
        public virtual Customer Customer { get; set; }
        public virtual ICollection<Product> Products { get; set; }
    }

    public class OrdersContext : DbContext
    {
        public DbSet<Company> Companies { get; set; }
        public DbSet<Customer> Customers { get; set; }
        public DbSet<Order> Orders { get; set; }
        public DbSet<Product> Products { get; set; }

    }

    public class Product
    {
        [Key]
        public int Id { get; set; }
        [StringLength(50)]
        public string Name { get; set; }
        public virtual ICollection<Order> Orders { get; set; }
    }
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("Saving customers");
            List<Customer> customers = new List<Customer>();
            List<Product> products = new List<Product>();
            Company company = new Company();

            customers.Add(new Customer()
            {
                Name = "Some name",
                Orders = new List<Order>()
                {
                    new Order()
                    {

                        Products = new List<Product>()
                        {
                            new Product() {Name = "Device1" },
                            new Product() {Name ="Device2" },
                            new Product() {Name = "Device3" }
                        }

                    },
                    new Order()
                    {

                        Products = new List<Product>()
                        {
                            new Product() {Name = "Device4" },
                            new Product() {Name ="Device5" },
                            new Product() {Name = "Device6" }
                        }
                    }
                }
            });

            customers.Add(new Customer()
            {
                Name = "Some other guy",
                Orders = new List<Order>()
                {
                    new Order()
                    {

                        Products = new List<Product>()
                        {
                            new Product() {Name = "Device7" },
                            new Product() {Name ="Device8" },
                            new Product() {Name = "Device9" }
                        }

                    },
                    new Order()
                    {
                        Products = new List<Product>()
                        {
                            new Product() {Name = "Device10" },
                            new Product() {Name ="Device11" },
                            new Product() {Name = "Device12" }
                        }
                    }
                }
            });


            using (OrdersContext context = new OrdersContext())
            {
                context.Companies.Add(company);
                context.SaveChanges();
            }
            using (OrdersContext context = new OrdersContext())
            {
                var customer = customers[0];
                customer.Company = company;
                context.Customers.Add(customer);
                int recordsSaved = context.SaveChanges();
                Console.WriteLine(String.Format("First customer saved {0} records", recordsSaved));
            }
            using (OrdersContext context = new OrdersContext())
            {
                var customer = customers[1];
                customer.Company = company;
                context.Customers.Add(customer);
                int recordsSaved = context.SaveChanges();
                Console.WriteLine(String.Format("Second customer saved {0} records", recordsSaved));
            }

            Console.WriteLine("Completed");
            Console.ReadLine();
        }
    }
}