public class Employee
{
    public int EmployeeId { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public List<ContactPhone> ContactPhoneNumbers { get; set; }
    public List<ContactEmail> ContactEmailAddress { get; set; }
}

public class ContactPhone
{
    public int ContactId { get; set; }
    public string Type { get; set; }
    public string Number { get; set; }
}

public class ContactEmail
{
    public int ContactId { get; set; }
    public string Type { get; set; }
    public string Number { get; set; }
}

EmployeeId  FirstName   LastName
_________________________________
1           Bala        Manigandan

ContactId   EmployeeId  Type    Number
__________________________________________
1           1           Fax     9123456789
2           1           Mobile  9123456789

ContactId   EmployeeId  Type    EmailAddress
______________________________________________
1           1           Private bala@gmail.com
2           1           Public  bala@ymail.com

DTO.Employee emp = new DTO.Employee()
{
    EmployeeId = 1,
    FirstName = "Bala",
    LastName = "Manigandan",
    ContactPhoneNumbers = new List<DTO.ContactPhone>
        {
            new DTO.ContactPhone()
            {
                Type = "Mobile",
                Number = "9000012345"
            }
        },
    ContactEmailAddress = new List<DTO.ContactEmail>()
        {
            new DTO.ContactEmail()
            {
                Type = "Private",
                EmailAddress = "bala@gmail.com"
            },
            new DTO.ContactEmail()
            {
                Type = "Public",
                EmailAddress = "bala@ymail.com"
            }
        }
};

public void ProcessEmployee(DTO.Employee employee)
{
    if(employee != null)
    {
        DevDBEntities dbContext = new DevDBEntities();

        DbContextTransaction dbTransaction = dbContext.Database.BeginTransaction();

        List<Task> taskList = new List<Task>();
        List<bool> transactionStatus = new List<bool>();

        try
        {
            Employee emp = dbContext.Employees.FirstOrDefault(m => m.EmployeeId == employee.EmployeeId);

            if (emp != null)
            {
                Task task1 = Task.Factory.StartNew(() =>
                {
                    bool flag = UpdateContactPhone(emp.EmployeeId, employee.ContactPhoneNumbers.FirstOrDefault().Type, employee.ContactPhoneNumbers.FirstOrDefault().Number, dbContext).Result;
                    transactionStatus.Add(flag);
                });

                taskList.Add(task1);

                Task task2 = Task.Factory.StartNew(() =>
                {
                    bool flag = RemoveContactPhone(emp.EmployeeId, "Fax", dbContext).Result;
                    transactionStatus.Add(flag);
                });

                taskList.Add(task2);
            }

            if(taskList.Any())
            {
                Task.WaitAll(taskList.ToArray());
            }
        }
        catch
        {
            dbTransaction.Rollback();
        }
        finally
        {
            if(transactionStatus.Any(m => !m))
            {
                dbTransaction.Rollback();
            }
            else
            {
                dbTransaction.Commit();
            }

            dbTransaction.Dispose();
            dbContext.Dispose();
        }
    }
}

public async Task<bool> UpdateContactPhone(int empId, string type, string newPhone, DevDBEntities dbContext)
{
    bool flag = false;

    try
    {
        var empPhone = dbContext.ContactPhones.FirstOrDefault(m => (m.EmployeeId == empId) && (m.Type == type));
        if (empPhone != null)
        {
            empPhone.Number = newPhone;
            await dbContext.SaveChangesAsync();
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }

    return flag;
}

public async Task<bool> RemoveContactPhone(int empId, string type, DevDBEntities dbContext)
{
    bool flag = false;

    try
    {
        var empPhone = dbContext.ContactPhones.FirstOrDefault(m => (m.EmployeeId == empId) && (m.Type == type));
        if (empPhone != null)
        {
            dbContext.ContactPhones.Remove(empPhone);
            await dbContext.SaveChangesAsync();
        }
    }
    catch (Exception ex)
    {
        throw ex;
    }

    return flag;
}