You are a flight assistant. 
 USER: Hi. I am George Nelson.

ASSISTANT: Hello, do you need any assistance from us?

USER: As my exam is postponed, I want to change my existing reservation. Can you help me?

ASSISTANT: I have found your reservation, please tell us your new trip dates.

USER: My airport codes are ORD to LAS.

ASSISTANT: Ok, may I know your travelling dates?

USER: My travelling dates are 07/25 to 07/27.

ASSISTANT: The UA airline with flight number 1009 is available having price as 100 and connection as 1.

USER: You can book it.

ASSISTANT: Ok, your reservation is done.

USER: Thank you for the quick service.

ASSISTANT: Thank you for choosing us.