answer: Lili is calling to thank Smith for the dinner and help in the past time.
documents: #Person1#: How do you do, Mr. Smith? This is Lili. I'm calling to thank you for the wonderful dinner we had yesterday. I enjoyed it very much.
  #Person2#: You're welcome. I'd like you to join us for dinner again sometime.
  #Person1#: Thank you, Mr. Smith. I'm returning to China today.
  #Person2#: Today?
  #Person1#: Yes. I appreciate all help and in particular, all the time that you've spent on my account during my stay here.
  #Person2#: Don't mention it. I am pleased to help you.
  #Person1#: If there's anything that I can help you in the future, please let me know.
  #Person2#: I'll do that. Thank you. Have a safe trip home.