Hello there. I am trying to locate a train for Monday. 
Sure.  Where will you be going?
I am going to Cambridge.
All right, and where would you like to depart from? 
I'll will be leaving from London Liverpool Street.
I've got 10 trains that are on that route. Do you have a preferred departure or arrival time? 
I need on that will leave London after 21:00.
I have two trains that will leave after 21:00. One leaves at 21:39 and one leaves at 23:39. Which would you prefer?
What time does the one that leaves at 21:39 arrive in Cambridge? Also, what is the train ID?
The train ID is TR5906 and it arrives by 23:07 in Cambridge. Would you like me to book that one for you?
No I don't need to book it right now. Thanks for the information. 
You're very welcome. Is there anything else I can help you with today?
Nope. Thanks though. Goodbye.
Let me know if you do need any more help. Good bye.