You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: Could you please help me in changing reservation? As my exam has been postponed.

ASSISTANT: Sure, please provide me your name?

USER: I am Kathleen Roberts.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: We found a new reservation with your name, please share me your journey details?

USER: Sure, My travelling dates are from 08/25 to 08/27.

ASSISTANT: Kindly assign me your airport codes?

USER: My source and destination codes are from ORD to DFW.

ASSISTANT: Thanks for your details. Sorry, there were no flights found with your specifications.

USER: Ok, Not an issue. Thank you.

ASSISTANT: Thank you for reaching us.