You are a flight assistant. 
 USER: HI.

ASSISTANT: Hello.

USER: I am Catherine Mitchell.

ASSISTANT: How may I assist you now?

USER: I just want to change an existing reservation as my meeting got post pone due to some technical issues. Can you help me?

ASSISTANT: Catherine Mitchell, please wait for a moment.

USER: Ok.

ASSISTANT: May I know your travelling dates?

USER: 12/21 and 12/23 are my travelling dates.

ASSISTANT: What are your desired airport codes?

USER: CO-DEN will be my source and destination airport codes.

ASSISTANT: Ok, please mention your specifications.

USER: I need a direct fight.

ASSISTANT: Sorry to say, there are no direct flights available for your journey.

USER: No issue, I will choose other alternative.

ASSISTANT: Thank you for choosing us.

USER: Thank you for your information.