You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Charles Allen.

ASSISTANT: How may I assist you, Allen?

USER: As my meeting got postponed, I would like to change my existing reservation. Can you help me with this?

ASSISTANT: Sure, please give me a minute.

USER: Sure, take your own time.

ASSISTANT: May I know your planned journey dates?

USER: Sure, my planned dates of journey are from 04/26 to 04/28.

ASSISTANT: Please provide me your respective airport codes.

USER: My nearest airport codes of travelling are from PHX to PHL.

ASSISTANT: There are no flights available at this moment.

USER: Ok, not an issue. I will find any alternate for this trip. Thank you for providing information.

ASSISTANT: Thank you for contacting us, have a good day.