I need to go to Datong to Erlian ( Mongolian border ) by bus

I know is the train, but it´s very expensive for me. I don´t know where is the bus station, maybe is Xinnan Passenger Transport Station or North Passenger Station? Also I don´t know is open or closed for Spring Festival those stations. Somebody told me is only one bus from Xinnan Passenger Transport Station early morning to Erlian, it takes 7-8 hours