public bool AddCustomer(Customer customer)
        {
            List <MobileOperator> mobileOperators = dataAccess.DisplayOperators();

            foreach (MobileOperator operatorr in mobileOperators)
            {
                try
                {
                    if (customer.OperatorId.OperatorId != 0)
                    {
                        DataAcces dataAccess1 = new DataAcces();
                        dataAccess1.AddCustomer(customer);
                    }
                }
                catch (InValidOperatorIdException)
                {
                    throw new InValidOperatorIdException("Enter valid operator id");
                }
            }
            return(true);
        }