I need to book a train for Monday from Ely to Cambridge to arrive by 14:00 for 6 people. 
What time would you like to leave by?
Anytime as long as i arrive by 14:00. Can you provide me with a reference number after booking? 
Great.  I booked six tickets on TR4095 departing at 11:35 and arriving in cambridge at 11:52.  Your confirmation number is W6PWPYOP. 
That is all I needed, good day to you. 
Have a great day!