I need a train on Friday, arriving by 12:15.
I can assist you with that.  Where are you travelling to and from?
I'm going from Cambridge to the Stansted Airport. 
The TR5998 leaves cambridge at 10:40 and arrives stansted airport at 12:08. It's price is 10.10 pounds. There are earlier trains if you wish.
That one sounds fine. Can you book it for 3 people? I will need the reference number too.
I have booked your ticket, the reference number is : ECTZFFR5. Is there anything else I can do for you.
Not at this time. Thank you so much for everything. Have a great day!
You are very welcome, goodbye.