I need a train to leave from London's Cross.
What day would you like the train for? 
I'd like it to be for Saturday.
I have a train that leaves London Kings Cross at 05:00 and arrives by 05:51 at a price of 18.88 pounds. Is that OK?
Yes, it is perfect. Thank you
I'm sorry I had that completely mixed up. There is a train leaving London Kings Cross at 5:17 and arriving in Cambridge at 6:08. Does that work?
Yes please book that and give me the reference number of the booking.
Yes I was able to book that and your reference number is XYVAABBJ. Cost of the ticket will be 18.88 pounds. Is there anything else?
No that will be all thank you.
Glad to help.  Have a nice day.  Good bye.