// Method which holds the interface for adding a customer to the crm file
        public void NewCustomerSubmenu(bool clear = true)
        {
            if (clear)
            {
                Console.Clear();
            }

            Console.WriteLine("### New Customer Submenu ###\n");
            Console.WriteLine("Please fill the following fields (fields with * are required)\n");
            Console.Write("Title*: ");
            title = StringToTitleCase(Console.ReadLine());
            Console.Write("FirstName*: ");
            firstName = StringToTitleCase(Console.ReadLine());
            Console.Write("LastName*: ");
            lastName = StringToTitleCase(Console.ReadLine());
            GenderValidationInput();
            DOBValidationInput();

            // Determine the highest ID number in the list
            int HighestID;

            // if the list has any customer, we determine the max ID using the max method on the list of objects
            if (Crm.CustomerList.Count() > 0)
            {
                HighestID = Crm.CustomerList.Max(Customer => Customer.ID);
            }// If the list has no customers, we make the id to be -1, so when the first customer is added, it will
            // increment by one, which will be 0 (-1 + 1 = 0).
            else
            {
                HighestID = -1;
            }

            // The customer id number must be unqiue, so we will make it equal to the highest ID number in the crm list and
            // increment it by one
            int CustomerIDNumber = HighestID + 1;

            // Add new customer
            Customer newCustomer = new Customer(CustomerIDNumber, title, firstName, lastName, Gender, DOB);

            if (Crm.AddCustomer(newCustomer))
            {
                Console.Write("\nSuccessfully created new customer '{0} - {1} {2} {3}' and added to customer list",
                              CustomerIDNumber, title, firstName, lastName);
                Crm.SaveToFile();
            }
            // If user presses any key, prompt the end of the menu
            LastMRRCscreen(() => SubMenu("Customer"), () => NewCustomerSubmenu());
        }