I got asnwer how to solve my probem i msdn forum: update appointments in one service call
I need to set property for one appoitment at the time and then add it to batch, after i set properties for all appointments i need to use _service.UpdateItems() method for my appointments batch:
pulic void UpdateAppointments(List<Item> _updateBatch)
{
Service.UpdateItems(upUpdateBatch, Folder.Id, ConflictResolutionMode.AlwaysOverwrite, MessageDisposition.SaveOnly, SendInvitationsOrCancellationsMode.SendToNone);
}