I need to book a train to travel to London Kings Cross leaving after 10:45.  Can you help me with this?
Sure! Where would you like to depart from? 
I'll be leaving Cambridge on Wednesday.
There are trains leaving at the hour throughout the day and night. If can book one of those for you if you like.
I need to leave after 10:45.
I can book you on TR9781 leaving Cambridge at 11 on Wednesday.  How many tickets should I reserve?
Can you book me 6 tickets please? I will also need the reference number too. 
I've reserved six tickets for you. Your reference number is X1C6NI79.
No, that will be everything. Thanks for your help.
You're welcome, enjoy your trip.