You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Rachel Martinez.

ASSISTANT: How can I help you today?

USER: Due to my ill health, I would like to change my existing reservation to Dallas. Can you help me with this?

ASSISTANT: Ok, please wait for a moment.

USER: Sure, take your own time.

ASSISTANT: Sorry Rachel, no reservation is found.

USER: Ok, not an issue. May be something went wrong while booking the ticket. Thank you for providing information.

ASSISTANT: Thank you for reaching us.