I'm looking for a train to cambridge on Saturday.
Where would you be departing from? 
I will be departing from Ely. 
Could you leave on Friday?  There are no trains available on Saturday from Ely to Cambridge.
Sorry, I misspoke. I am actually departing from Broxbourne. 
There are about 19 trains available. I can narrow that down some if you tell me if you want to leave or arrive by a certain time. 
I would like to arrive by 15:30.
There are 9 trains that meet your criteria that day, one leaving every hour from 05:32. Do you have a departure time preference?
No, we just want to get there either at or right before 15:30, please. Can you get me 8 tickets on the closest train to that time?
8 tickets for the TR7846 leaving at 09:32 your reference number is D0CG7JD3. Anything else today?
I'm sorry, I meant that I need 5 ticket for the train booked. Can you fix this? 
Yes sure. I booked that for you for 5 people and the reference number is  IFXPNYHS.