Train Tickets Booking from Overseas

Dear All,

We plan to visit China for our business purposes. I read in some travel tips websites in my country, Iran that if you buy tickets from your country the one who has made the payment should be with you during your trip. I am from Iran and as you know I cannot make direct payment through my Master card or Visa card because of sanctions. I can just make them through western union. Please confirm that the one who has bought the tickets for us should not be necessarily with us on the trip. How can you help us for buying the internal tickets ? Can we pay through western union?
Best Regards,
Mohamad