Is there an office at Beijing INT. A/P where I can buy air/train tickets

Is there an office at Beijing INT. A/P where I can buy air/train tickets? Will it be open at 0500 am - 0600 am. Since I'm looking for the same day tickets (either air or train). We are arriving to Beijing A/P from an International flight, which is scheduled to land at 0440 am. And I can NOT be sure whether the incoming flight will not be late, and besides we wish to proceed directly (without entering Beijing) to our 1st destination in China.
Much obliged
Eli ( Israel )